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It is becoming more apparent that the aquatic carnivorous plants Utricularia (Lentibulariaceae) can capture and utilise a wide range of small aquatic organisms. Although they can take up nutrients directly from the water by rootless shoots, much of their overall nutrition comes from prey caught in their traps. Most of the early literature was focused mainly on animal prey, hence the term carnivorous to describe Utricularia spp., but more recently the contribution of other microorganisms and detritus to their diet is being realised. Specifically, the importance of the phytoplankton in traps as prey is proving interesting. However, most investigations have focused on the trap communities with few comparisons to phytoplankton as potential prey, which could reveal the occurrence of feeding selectivity. The eurytopic species Utricularia australis was surveyed across 12 sites in central Italy in lentic waterbodies ranging from oligotrophic to eutrophic. Phytoplankton communities outside the traps were composed of 135 taxa from 21 orders belonging to eight phyla and the algal community in the traps comprised 124 taxa from 17 orders belonging to eight phyla, recorded from all sampling sites. Among the 12 sites phytoplankton communities were highly diverse; however, communities inside and outside the traps at each site were very similar. This similarity indicated that feeding was not selective. Algal movements are not able to elicit a trap response, yet around 70% of the traps contained phytoplankton only (no animal prey). Therefore, regular spontaneous trap firing, known to occur in U.australis, is thought to be responsible for the similarities in trap and plankton algal communities. At two sites, a Euglenophyte (Lepocinclis sp.) and a Cryptophyte (Chilomonas sp.) proliferated, which were otherwise very rare in the phytoplankton community. This is indicative of favourable growth conditions in the traps and possibly of commensal relationships. It seems that the diet requirements of U.australis are met by having a highly varied prey spectrum.

Among the freshwater cyclopoids, small and medium-sized species can be propagated in the laboratory with a flagellate Chilomonas as the food. By contrast, large species need to be given, in addition to the flagellate, a larger food organism. For this, although a metazoan food is preferable, a ciliate Stentor may in part serve as a substitute. Methods for infection experiment involving copepods are given, and photographs of some parasite larvae in the copepod host are shown. Usage of carbonated water is helpful to immobilize cyclopoids and thus recommended for infection experiments.

This study aimed to investigate the distribution and abundance of plankton in the downstream area of Jeneberang River. A total of three observation stations were chosen through purposive sampling method on a watershed in the downstream area, which lies between Gowa Twin Bridge and Barombong Bridge, Takalar Regency, and Makassar City. At each station, a sample was taken from the northern (N) and southern (S) part of the river. The collected sample of Plankton was observed using a binocular light microscope and Sedgwick Rafter Counting Cell (SRCC), and then subjected to the identification by using plankton identification book. The result of data analysis showed that phytoplankton and zooplankton could be found in all observation stations, but the abundance and distribution of each group differed one another. Phytoplankton group with the highest to the lowest abundance is the member of Class Chlorophyceae, Bacillariophyceae, and Dinophyceae. Meanwhile, the commonly found zooplankton is the member of Protozoa, including Paramecium sp., Chilomonas sp. Besides that, the member of Animalia, including annelid larvae and polychaeta larvae were also found with a lower level of abundance.

We investigated the direct utilization of fine particulate detritus (dried and homogenized plant material in the size range of bacteria) as a food source for protozoans using axenic cultures of the cryptomonad, heterotrophic flagellate, Chilomonas paramecium, and the hymenostome ciliate, Tetrahymena pyriformis. When fed media containing only particulate detritus, these species revealed growth rates similar to those reported for field populations. The growth rates of Chilomonas fed exclusively particulate detritus were similar to those obtained on a bacterial diet. Considering the high percentage of detritus particles in the size range of bacteria in lakes, our results imply that direct utilization of detritus by protozoans may form an additional pathway of carbon in aquatic food webs that has generally been overlooked.

Seventy-three strains of cryptophytes assigned to the genera Cryptomonas, Campylomonas or Chilomonas were studied by light microscopy, spectrophotometry and whole-mount electron microscopy. Twelve groups of strains were distinguished by light and whole mount electron microscopy using a combination of characters, mainly cell size, type of periplast and presence/absence and number of pyrenoids. However, characters previously used to distinguish Cryptomonas from Campylomonas (e.g. the type of periplast: polygonal periplast plates vs. a continuous periplast sheet) were found to occur together in dimorphic strains, indicating that periplast types relate to different life-history stages of a single taxon. To evaluate the taxonomic significance of the type of periplast and other characters previously used to distinguish genera and species, representatives of each strain group were subjected to molecular phylogenetic analyses using two nuclear ribosomal DNA regions (ITS2, partial LSU rDNA) and a nucleomorph ribosomal gene (SSU rDNA). The results of the phylogenetic study provide molecular evidence for a life history-dependent dimorphism in the genus Cryptomonas: the genus Campylomonas represents the alternate morph of Cryptomonas. Campylomonas and Chilomonas are reduced to synonyms of Cryptomonas, the genus Cryptomonas is revised and typified, two new species are described and six species are emended.

An unknown parasitic protist is described in the free-living cryptophyte Chilomonas paramaecium. The biflagellated sporozoite has an elongated shape with an apical complex and a central nucleus. The pair of flagella are inserted at the base of the pseudo-conoid, and two microtubular roots situated underneath the plasma membrane are attached to each basal body. The apical complex comprises a set of 10-14 micronemes and a train of dumb-bell vesicles which converge toward the tip of the pseudo-conoid. Micronemes are outlined by a four-microtubule fibre and the train of vesicles is associated with a three microtubule in a rake-like fibre. The mitochondrial network has few cristae and a fairly reduced dense matrix. A large vacuole containing microfilamentous material is connected to the nuclear envelope and the Golgi body is situated close to the nucleus. The life cycle begins with the adhesion of the anterior tip, followed by the penetration of the flagellated sporozoite in a specialized region at the base of Chilomonas flagella. The trophont grows within the host cytoplasm, and after 4-5 successive nuclear mitoses, the trophozoites/sporozoites bud on the surface, while they acquire flagella, micronemes and other apical structures. The mitosis is closed with an external spindle lacking a paradesmosis. There is no sporangium, but a resting-cyst was sometimes observed inside the host. This parasite is phylogenetically affiliated to the Perkinsozoa lineage comprising Perkinsus and Parvilucifera. The new genus Cryptophagus is created for this parasite.

We tested the influence of different types of food on the fitness of Daphnia longispina during a period of poor resources by comparing the growth and reproduction of individuals fed on different diets. When Daphnia were under starvation conditions, both dissolved organic carbon and metabolic products enhanced bacterial growth, and the cladoceran produced 15 neonates and survived for the 55 days of experiment. In the natural water, the edible food consisted essentially of bacteria and heterotrophic flagellates, which enabled the cladoceran to grow and reproduce. In water enriched with Cryptomonas (an alga) or Chilomonas (a heterotrophic flagellate), the daphnid growth rates increased considerably from generation to generation, but later in the time course of the experi- ment with Chilomonas than with Cryptomonas. This alga enhanced the phosphorus:carbon ratio. The primiparous daphnids fed with Cryptomonas were smaller than those fed with the heterotrophic flagellate and enrichment with the heterotrophic flagellate also enhanced reproduction. In Lake Tazenat, when the algal biomass was insufficient to support the Daphnia life cycle, the heterotrophic organisms were an essential food source. When feeding essentially on bacteria, Daphnia has the capacity to grow and reproduce at very low food concentrations, and this is important in determining its fitness under competitive conditions.

Assuming that heterotrophic flagellates (H.F.) can sustain cladoceran life cycles, particularly at periods of low food and high detritus conditions, the growth, reproduction and life span of Daphnia longispinawere studied under conditions of summer food limitation. They were fed both natural resources and natural food enriched with a culture of the colourless Chilomonas (ovoid cell, 8 × 25 μm). Four H.F. morphotypes occurred in the natural water and the first experiments with Daphnia, showed that the cladoceran would most easily ingest those of 5 μm–10 μm, while the addition of Chilomonas severely depressed the H.F. of 2 μm. The capability of this flagellate to ingest small H.F. was confirmed using fluorescent particles ranging from 0.94 to 3.95 μm. As a consequence, Daphnia could control the abundance of H.F., but also compete with the largest morphotypes. To study the influence of the H.F. on the life span of Daphnia, the cladoceran was acclimated for two generations, before the start of the experiments. In semi-natural conditions, constant temperature, without predators and fed natural water, the summer daphnids achieved smaller sizes, produced fewer offspring and lived for a shorter time than when Chilomonas was added to their diet. Despite the addition of 560 μg C l-1, this was not sufficient to enhance the Daphnia reproduction to the level of the spring population fed natural water. These results clearly illustrate that the heterotrophic flagellates contributed significantly to improving the reproduction and survival of the daphnids. They emphasise the importance of the microbial loop as a link to larger consumers, particularly when unpalatable or nutritionally inadequate algae are dominant, which is often so in lakes during summer.

The Cryptophyta comprise photoautotrophic protists with complex plastids which harbor a remnant eukaryotic nucleus (nucleomorph) and a few heterotrophic taxa which either lack a plastid (Goniomonas) or contain a complex plastid devoid of pigments (Ieucoplast; Chilomonas). To resolve the phylogenetic relationships between photosynthetic, leucoplast-containing and aplastidial taxa, we determined complete nuclear-encoded SSU rRNA-sequences from 12 cryptophyte taxa representing the genera Cryptomonas, Chilomonas, Rhodomonas, Chroomonas, Hemiselmis, Proteomonas and Teleaulax and, as an outgroup taxon, Cyanoptyche gloeocystis (Glaucocystophyta). Phylogenetic analyses of SSU rRNA sequences from a total of 24 cryptophyte taxa rooted with 4 glaucocystophyte taxa using distance, parsimony and likelihood methods as well as LogDet transformations invariably position the aplastidial genus Goniomonas as a sister taxon to a monophyletic lineage consisting of all plastid containing cryptophytes including Chilomonas. Among the plastid-containing taxa, we identify six major clades each supported by high bootstrap values: clade I (Cryptomonas and Chilomonas), clade II (Rhodomonas, Pyrenomonas, Rhinomonas and Storeatula), clade III (Guillardia and the 'unidentified cryptophyte' strain CCMP 325), clade IV (Teleaulax and Geminigera), clade V (Proteomonas) and clade VI (Hemiselmis, Chroomonas and Komma). Clade I (Cryptomonas and Chilomonas) represents a sister group to clades II-VI which together form a monophyletic lineage; the phylogenetic relationships between clades II-VI remain largely unresolved. Chilomonas is positioned within the Cryptomonas clade and thus presumably evolved from a photosynthetic taxon of this genus. In our analysis the characters blue and red pigmentation do not correspond with a basal subdivision of the phylum, thus rejecting this character for higher-level classification of cryptophytes. However, different spectroscopic subtypes of phycoerythrin (PE I-III) and phycocyanin (PC II-IV) represent informative characters at a lower taxonomic level. Phycocyanin types are confined to the later diverging clade VI and within Hemiselmis, a species with phycocyanin is monophyletic with two species containing phycoerythrin. This supports previous molecular studies which demonstrated that the β subunit of all cryptophyte biliproteins, regardless of spectroscopic type, is phylogenetically derived from the red algal β-phycoerythrin gene family, therefore the cryptophyte phycocyanins presumably originated by chromophore replacement from phycoerythrin. Our phylogenetic analysis does not support a previous suggestion that the aplastidial cryptophyte Goniomonas evolved from an ancestor containing a complex cryptomonadtype plastid by nucleomorph and plastid loss.

Nuclear and nucleomorph 18S ribosomal RNA genes from six cryptomonads were amplified by the polymerase chain reaction and sequenced. Phylogenetic trees were constructed by distance, parsimony, and maximum likelihood methods for all available cryptomonad nuclear and nucleomorph 18S rRNA sequences. Nuclear and nucleomorph trees are largely congruent and clearly disprove the idea of polyphyletic origins for cryptomonad chloroplasts. Both show the leucoplast-containing Chilomonas as the sister to all photosynthetic cryptomonads. Using 11 cryptomonad nucleomorph sequences gives more convincing evidence than before that cryptomonad nucleomorphs originated from a red alga and are not specifically related to Chlorarachnion nucleomorphs. Both trees show as a clade the genera with nucleomorphs embedded in a chloroplast-envelope invagination into the pyrenoid (Storeatula, Rhinomonas, Rhodomonas). This monophyly of embedded nucleomorphs supports the recent creation of the order Pyrenomonadales for such cryptomonads. ...

Summary New ultrastructural data on the flagellate Leucocryptos marina (Braarud) Butcher 1967 (= Bodo marina Braarud 1935 = Chilomonas marina Halldal 1953), the type species of Leucocryptos Butcher 1967, show that this is not a cryptomonad as previously supposed. L. marina has tubulocristate mitochondria, a surface sheath, three new types of extrusomes, a cytoskeleton composed of pellicular microtubular bundles, and a cytostome associated with: 1) vesicles, 2) a cytopharyngeal cylinder of microtubules and 3) the cytoskeleton. Katablepharis/Kathablepharis ovalis Skuja 1948, another heterotrophic flagellate, is similar in ultrastructure. K. hyalums Skuja 1939 resembles these species, but lacks a cytostome. The status of Katablepharis/Kathablepharis and Leucocryptos is discussed, and the family Katablepharidaceae (ICBN) or Kathablepharidae (ICZN) is redefined. Leucocryptos marina is a phagotrophic nanoplankton predator. New data on its occurrence and abundance and a summary of previous records are presented. L. marina may be found during all seasons, but it attains highest numbers in coastal waters with high phytoplankton production. Autecological experiments and field data show that the flagellate is euryhaline and eurythermal and with a cosmopolitan distribution.

Ecological theorists propose that the species composition of trophic levels can influence the relative strengths of top-down (predation) or bottom-up (nutrient) effects in food chains. We tested this by constructing two- and three-level food chains of bacteria and protists. Bacteria made up the first trophic level. The second level contained Chilomonas paramecium alone, Colpidium cf. striatum alone, or both together. Predatory Euplotes patella occupied the third trophic level. These assemblages were cultured in microcosms containing either low- or high-nutrient medium. Manipulating nutrients and predation produced comparable changes in the abundance of bacteria. In the second trophic level, Chilomonas was usually driven extinct by predation, but Colpidium was affected more by nutrients than predation because it had a partial size refuge from predation. Both species survived more poorly with predatory Euplotes if the other was present, because the predator was more abundant and persistent when both prey were available. The predator was less persistent in high-nutrient microcosms, because additional nutrients boosted the proportion of Colpidium populations within the size refuge. This type of mechanism could limit trophic cascades in food chains where resources affect prey vulnerability.

Increased complexity in biological communities can increase the variety of interactions among species, but the relative strengths and long-term consequences of various direct and indirect interactions require further investigation. I studied interactions among four species of protists by monitoring their population dynamics when they were cultured either together or in seven different subset communities. Two protists were bacterivores (Chilomonas and Tetrahymena) and two were predators (Actinosphaerium and Euplotes). Actinosphaerium was omnivorous, and could eat both predatory Euplotes and bacterivores. Three indirect effects occurred among the four species of protists, including indirect facilitation of one predator by the other, apparent competition between bacterivores, and indirect facilitation of one bacterivore by the omnivorous predator. Community structure and invasibility depended on both direct and indirect effects; thus both can be mechanisms for assembly rules.

In the protozoan class Phytomastigophorea, the 5 S rRNA sequences from three species, Crypthecodinium cohnii (order Dinoflagellida), Euglena gracilis (order Euglenida) and Chlamydomonas reinhardii (order Volvocida), are known. These 5 S rRNAs do not show any striking similarity to each other, suggesting that these orders, although classified in the same class Phytomastigophorea, are only remotely related to each other. Here, we have determined the sequence of 5 S rRNA of another Phytomastigophorea species, Chilomonas paramecium (order Cryptomonadida), and compared it to those of the other species of the same class as well as of other eukaryotes to deduce the phylogenie position of Chilomonus. The Chilomonas sequence shows a fairly low but almost equal similarity to the sequences of the other Phytomastigophorea species and also to those of other protozoa, plants, fungi and animals.

The behaviour of contractile vacuole complexes of representatives of the Cryptophycean genera Chilomonas, Cryptomonas, Cyathomonas and Rhodomonas is described using light and electron microscopy. The contractile vacuole occupies a fixed position in the cell, lying adjacent to the flagellar pocket/groove. A small region of the flagellar pocket is invaginated so that the plasma membrane lies close to the membrane of the contractile vacuole. This region acts as the pore through which the contents of the contractile vacuole are discharged. Discharge follows the fusion of the contractile vacuole membrane with the plasma membrane of the pore. Filling initially involves the fusion of small vacuoles which appear around the contractile vacuole shortly before the discharge of its contents. After these vacuoles have fused, filling may continue by the accretion of small vesicles which form the spongiome surrounding the contractile vacuole. Two types of vesicles have been identified in the spongiome. One type is invol...

The extracellular starch released by autolysis of glycerol-grown Chroomonas salina (Wislouch) Butcher was purified and chemically characterized. It contained 99%D-glucose, formed a blue complex (λmax at 605 nm) with iodine, and showed an optical rotation value more positive than that of potato starch. Methylation analysis established the presence of 1,4- and 1,4,6-glucoside linkages in the proportion 15:1. These properties indicate the cryptomonad starch to be an iodophilic α-(1,4)-glucan, composed of ca. 30% amylose with amylopectin, and broadly resembling potato, Chilomonas and other unicellular algal starches.

Summary The unique and diagnostic characteristics of the Cryptophyceae are discussed and present knowledge of their taxonomy is summarized. It is proposed that the pigmented organisms can be assigned to four genera, Hemiselmis, Chroomonas, Cryptomonas and Pyrenomonas nom. nov.; the characteristics of these genera are reviewed. The validity of the pigmented genera Isoselmis, Plagioselmis and Rhodomonas and the apochlorotic genera Chilomonas, Cyathomonas and Phyllomitus is considered and present knowledge of their taxonomy is summarized.

Summary The principal feature of recent studies on the nutrition of the Protozoa has been the development of culture media suitable for the maintenance of several score of species in ‘pure culture’. As investigators approached precise definition of the constitution of the culture media the significance of ‘trace elements’, accessory food factors and the like became more apparent. The types of culture apparatus, the methods of sterilization of organism and medium, the procedures of estimating growth of populations, and the exact composition of reagents have all been found to be of greater importance than originally realized. Within the phylum there exist chlorophyll-bearing, plant-like forms and numerous intermediary types up to and including those requiring living particulate food, thus providing the full range of nutritional types. The older systems of physiological classification have been extensively revised, but none of those proposed is adequate. In some instances the relations between variations in cytoplasmic structure (plastids) and nutritional requirements have been demonstrated. Many species of chlorophyll-bearing and colourless flagellates have been studied. Intensive work on Polytoma, Chilomonas and Euglena has revealed notable species and strain variations with respect to factors such as fatty acid metabolism, nitrogen requirements, the effects of light on nutrient requirements and on response to plant hormones and vitamin constituents. The effect of systematic modification of chemical structure on the utilization of vitamin components has been studied for some species. A few dozen of the normally phagotrophic (holozoic) forms have been grown in the absence of other living forms (pure liquid culture), while certain forms have been grown on single species of food organisms (pure mixed culture) or on dead food organisms. With the exception of certain amoebae the salient work on pure culture has been carried out with the smaller ciliates, particularly Glaucoma. The media employed (protein hydrplysates, tissue autolysates, etc.) are chemically and physically highly complex. Such media contain labile constituents susceptible to important changes when subjected to minor procedural variations. Analyses of the media before and after the growth of organisms have given some indications of the nature of the nitrogenous fractions metabolized. The accessory growth-factor requirements of these forms are complex. The very specialized nutrients required by parasitic forms have demonstrated interesting evolutionary relationships. An increasing number of biochemical experiments is being reported on the existence of various enzyme systems in the Protozoa. Our knowledge, however, of the metabolism of representative Protozoa remains fragmentary.

Chlorogonium (euchlorum, elongatum) is capable of indefinite autotrophic growth in a mineral medium in light, growth in nitrate being as good as in cultures containing ammonium salts. It was impossible to maintain bacteria-free cultures of Chilomonas paramecium indefinitely by subculturing them at regular intervals in a medium containing inorganic nitrogen, even in the presence of sodium acetate as a carbon source. Since November 10, 1932, both species of Chlorogonium have been cultured in total darkness in a medium containing mineral salts, sodium acetate, dextrose and proteose-peptone without losing their green color.

1. Examination of the contractile vacuole of Chilomonas paramecium during progressive impregnation by the Weigl osmic technique revealed that the so-called ‘osmiophil cortex’ appeared first as a number of perivacuolar osmiophilic granules. Prolonged impregnation caused these to fuse to form a closed ring which, after very prolonged incubation, became a solid osmiophilic mass. 2. Cultures fixed together and osmicated in separate tubes gave more consistent impregnations, in any one series, than those both fixed and osmicated separately. 3. With the two samples of osmium tetroxide used, after normal fixation, A consistently gave impregnations of 62-85 per cent., and C impregnations of 25-36 per cent. 4. Constant mixing during fixation and osmication was not advantageous, and gave more irregular results than normal methods. 5. Time of fixation, between the limits of 5 to 90 minutes, had no effect on the impregnation. 6. It was suggested that the irregularities of impregnation with a given sample of osmium tetroxide were due to the presence of a trace of some retarding agent, possibly introduced at the time of fixation. 7. It was shown that the osmiophily of the perivacuolar region in Chilomonas did not vary with the vacuolar phase.

1. Experiments were performed to ascertain the effect of vanadium (VOCl2 and Na3VO4), copper (CuCl2), manganese (MnCl2) and iron (FeCl3) in acetate-ammonium solution on the rate of reproduction and the synthesis of starch and fat in Chilomonas paramecium.2. Tetravalent vanadium in VOCl2 causes marked increases in the frequency of division in Chilomonas which vary with the concentration. As the concentration of VOCl2 added to the acetate-ammonium solution was increased, the frequency of division increased to a maximum at approximately 10-5 M and then decreased. Pentavalent vanadium in Na3VO4 causes no increase in frequency of division. Tetravalent vanadium at certain concentrations is therefore beneficial for growth of Chilomonas and pentavalent vanadium is not.3. Neither copper, manganese nor iron in acetate-ammonium solution causes any statistically significant increase in the frequency of division of Chilomonas, and neither manganese nor iron causes a significant decrease in the frequency of division, b...

SYNOPSIS Axenic cultures of Chilomonas paramecium were grown in media lacking a C-source, resulting in breakdown in autophagosomal vesicles of large numbers of trichocysts. Return of the starved organisms to complete media was followed by a wave of trichocyst formation. Stages in the degeneration and subsequent reformation of trichocysts are described as well as attempted labeling of the developing organelles with 3H-thymidine. A modification of the method of Anderson et al. (2) was used for isolating quantities of exploded trichocysts from Chilomonas. Attempts at isolation of the trichocyst in its coiled state were unsuccessful. Isolated trichocysts mounted on electron microscope grids were subjected to various types of enzymatic digestions.

1. The effects of O2, CO2, and pressure were studied in two very different species of protozoa, a flagellate, Chilomonas paramecium, grown in acetate-ammonium solution and a ciliate, Tetrahymena geleii, grown in 2 per cent proteose-peptone solution. 2. Chilomonas and Tetrahymena live and reproduce in solutions exposed to a wide range of O2 concentrations, but Chilomonas is killed at high O2 tensions in which Tetrahymena grows best. The optimum O2 concentration for Chilomonas is about 75 mm. pressure but it lives and reproduces in O2 tensions as low as 0.5 mm. while Tetrahymena fails to grow in concentrations below 10 mm. O2 pressure. 3. With a constant O2 tension of 50 mm. pressure, it was found that there is no significant variation in growth in Chilomonas between 50 mm. and 740 mm. total pressure. In Tetrahymena, however, under the same conditions, an optimum total pressure was found at about 500 mm. and growth is comparatively poor at 50 mm. total pressure. 4. Tetrahymena does not live very long in CO2 tensions over 122 mm., although Chilomonas grows as well at 400 mm. CO2 as in air at atmospheric pressure (0.2 mm. CO2). Tetrahymena grows best in an environment minus CO2, but the optimum for Chilomonas is 100 mm. CO2 at which pressure an average of 668,600 ± 30,000 organisms per ml. was produced (temperature, 25 ± 1° C.). 5. Chilomonads grown in high CO2 concentrations (e.g., 122 mm.) produce larger starch granules and more starch than those grown in ordinary air at atmospheric pressure. 6. In solutions exposed to 75 mm. O2 tension (optimum) and 122 mm. CO2 plus 540 mm. N2 pressure, chilomonads contain very little, if any, fat. This phenomenon seems to be due to the action of CO2 on the mechanisms concerned with fat production. 7. In Tetrahymena exposed to pure O2, there is very little fat compared to those grown in atmospheric air. This may be due to the greater oxidation of fat in the higher O2 concentrations. 8. Further evidence is presented in support of the contention that Chilomonas utilizes CO2 in the production of starch.

In mixed cultures, where Tetrahymena patula preys on Chilomonas paramecium, the growth of the Chilomonas population does not initially differ significantly from that in single cultures. Later, however, the decrease in numbers of Chilomonas is more rapid in mixed cultures, where it dies out after two months. The composition of the polymorphic Tetrahymena patula population depends on age and on the presence or absence of Chilomonas. Slit-mouthed forms are absent at the beginning of growth in both mixed and single cultures, and only appear subsequently in mixed cultures. The percentage of these forms increases in older cultures. The percentage of microstomatous forms is larger, however, at the beginning of population growth, both in mixed and single cultures. The percentage of macrostomatous forms increases from the beginning, reaches a maximum, and then decreases. Cannibalism has been observed in old mixed cultures. Significant differences in the size of individual organisms of Chilomonas between single and mixed cultures appeared from the beginning of the logarithmic phase of growth, and were pronounced up to the end of observations. Significant differences in the size of Tetrahymena patula between single and mixed cultures appeared somewhat later, from the sixth day onwards. The differences in size and shape between organisms in cultures of the same kind but of different ages were also significant. Variation in size and shape of both species was greater in mixed than in single cultures.

1. In Chilomonas paramecium the contractile vacuole is surrounded by a cortical substance (Golgi apparatus) which has the power of reducing osmium tetroxide solution and thus impregnating black (Nassonow). 2. This cortex blackens thus in over 99 per cent, of individuals in a culture which has not been dividing. In a culture in which the individuals have been rapidly dividing, the percentage of unimpregnated contractile vacnoles increases considerably, up to about 5 per cent. 3. During division of Chilomonas in about 70 per cent. of cases the osmiophile substance is very equally divided between the daughter cells. The dividing cortex comes away from the contractile vacuole, which eventually collapses, new contractile vacuoles arising in the site of the divided osmiophile material. In about 25 per cent, of division stages osmication of the cortex fails to a greater or lesser degree. There is always a very distinct tendency for this failure to take place even in the best of preparations. 4. In some cases (about 3 per cent.), during division, the entire contractile vacuole and its cortex goes over whole to one individual. A new vaeuole, apparently without cortex, arises spontaneously in the other individual. It is unlikely that all of these cases are due to failure of impregnation in one of the individuals, though this possibility cannot be roled out completely. 5. The behaviour of the original contractile vacuole cavity before separation of the daughter cells is as follows. The lipoid, having partially retreated from the vacuole, becomes separated into two parts, and the centrally placed vacuole disappears (figs. 4 and 6, Pl. 36; figs. 10 and 15, Pl. 37). New vacuoles appear in the site of the lipoid bodies in each daughter cell (fig. 5, Pl. 36). 6. Two ellipsoidal accessory bodies or pyrenoids lie on a level with the vestibule. In older cultures the two bodies are often exactly the same size and colour (corrosive osmic followed by neutral red or haematoxylin), but in rapidly dividing cultures, one body may be of normal size, whereas the other may be absent or much smaller. During cell division, one body is carried across to each daughter. No exception to this was ever found. 7. Identification of the smaller Peranemidae is in a confused state. Probably several species, and possibly even genera, have been described by various authors as Scytomonas (Copromonas) subtilis.

ONE OF THE MOST striking features of phytoplankton populations in the sea is fluctuation both in the type and in the number of cells present. Study of plankton hauls has revealed a seasonal flowering of diatoms, and the factors promoting their growth have long been objects of study (Harvey, 1939; Gran, 1930; Riley, 1947). The number and species of dinoflagellates also vary enormously, although these fluctuations are perhaps less perfectly correlated with time of year than in the case of the diatoms. The physiological factors which lead to rapid multiplication of dinoflagellates are poorly understood. The purpose of this investigation was to determine what chemical factors are necessary for rapid growth of these organisms in culture. It is known that the multiplication of certain other plankton organisms in culture is much accelerated by the addition of soil extract to the culture medium. Such extracts were first used extensively in culture media for algae by Pringsheim (1912). Since that time, soil extracts have been widely successful in promoting the culture of organisms that are difficult to grow in inorganic media (diatoms, Harvey 1939; flagellates, Lwoff and Lederer, 1935). The active principle in soil extract has not been identified with respect to any of these organisms. However, Pringsheim (1936), on the basis of experiments employing Chlorogonium, Polytoma, Polytomella, and Chilomonas as test organisms, has concluded that the active principle is an acidand alkaline-stable organic substance, insoluble in alcohol and ether, adsorbed by charcoal, and destroyed by hydrogen peroxide. Whatever the nature of this principle, it is evidently important in the nutrition of a fairly wide range of unicellular organisms. Thus it seemed profitable to begin this investigation with a detailed study of the effect of soil extract on the rate of growth of dinoflagellates. HISTORY OF THE CULTURE OF MARINE DINOFLAGELLATES.-The literature contains few records of marine dinoflagellates which have been maintained in culture for many transfers. A number of species have been cultured for short times by taxonomists who wished to identify the organisms or follow their life cycles. These cultures were usually not bacteria-free and were sometimes mixtures of several species, and no attempt was made to determine optimum conditions for growth. Kiister (1908) grew Gyrodinium jucorum for a period of

Chilomonas undergoes no respiratory adaptation to growth temperature, although there is a marked size adaptation. Thus, there is probably no intimate association of mechanisms of adaptation in respiration and size where both are found in the same organisms. Neither total membrane area nor “dilution” of the cell have had a demonstrable effect upon Chilomonas' respiration. The Q 10 for oxygen consumption over the range of 15 ° to 25 °C is 2.8 for any culture, regardless of its growth temperature.

1. When the three species of free-living flagellates employed in this investigation are subjected to the high centrifugal force obtained by the use of the air-driven centrifuge, stratification of the cytoplasmic components and inclusions takes place. 2. This stratification is most noticeable in the chlorophyll bearing Euglena. The chloroplasts form a belt having on the centrifugal side paramylum and neutral-red bodies, while the clear cytoplasm containing small spherical bodies, probably mitochondria, is at the centripetal pole 3. This stratification is a temporary process. Complete redistribution of the parts can take place. The orientation of the stratification is not dependent on the morphological polarity of the organism. The heaviest components may occupy the anterior, posterior, or lateral part of the organism. 4. There is no evidence that the bodies which stain intra vitally with neutral red are homologous with the Golgi bodies of the metazoa. On the contrary there is some new evidence to support the findings of Baker (1933) that these bodies stainable with neutral red give a metachromatic reaction with Meyer's methylene-blue method, and are therefore probably identical with volutin. We have reached no satisfactory conclusion regarding what structures represent the Golgi apparatus. The theories put forward by other observers are briefly discussed. 5. Fixatives containing osmic acid show spherical bodies close to the periphery of the organism. They are not moved by the centrifugal force. 6. Short notes are given on the effect of the ultra-centrifuge on Menoidium sp. and on Chilomonas paramecium. As in Euglena the heaviest materials in Menoidium are the paramylum and bodies stainable with neutral red. In Chilomonas starch grains and neutral-red-stainable bodies are displaced to the centrifugal pole. In control specimens of Menoidium there is sometimes a natural stratification to be observed the paramylum and neutral-red bodies being gathered together usually at the anterior end of the organism.

The effects of formalin, Lugol's iodine solution and a mixture of these preservatives on the cell volumes of two protozoan species (the flagellate Chilomonas sp. and the ciliate Cyclidium sp.) were studied using phase contrast microscopy. While the percent of live volume was affected by the preservative used and protozoan type, storage time was of overriding importance. Within 10 min., cells exposed to formalin and formalin + Lugol's solution increased in biovolume, but by 24 h cell shrinkage was in the range of 6 – 19% of live biovolume, formalin fixed samples having the least amount of shrinkage. After one month of storage, cell biovolume was reduced to between 60 and 65% of live biovolume in all three preservatives.

SUMMARY. Isolated Blepharisma undulans were studied for the following: (1) fission rate, (2) mating behavior, (3) giant formation, (4) effects of daily transections. The organisms were maintained at 22°C. and isolated daily for 60 days. Fission rate varied from two divisions a day to one in 29 days. The major factor producing the variation appeared to be the type or amount of food. Frequency of conjugation also varied greatly. Daughters of a single organism will mate within 24 hours after division. Conjugation followed by one division, re-isolation, then conjugation within 24 hours following a second division occurred within a 5 day period. Giants were produced within 3 days by feeding with Khawkinea, Chilomonas and Paramecium. Paramecium alone did not produce giants. Exposure to 10−m, 10−4M colchicine did not accelerate this process. Daily transections into approximately equal halves were made. The anterior halves containing the mouth membranelles were followed. Fission rate was not affected by cutting. A progressive decrease in size occurred. All ultimately lysed, most on the 7th day. If cutting was suspended on any day, recovery and fission followed. If cutting was re-instituted, lysis would again occur on or about the 7th day. Daily amputation of the posterior tip for 2 weeks did not affect either size, fission rate, or longevity.

SYNOPSIS. Chilomonas paramecium contains 2 different fatty acid activating enzymes (FAAE), one of which utilizes acetate as a substrate, while the other catalyzes the reaction with either butyrate or hexanoate. The site of greatest activity of these enzymes was found to be not in the mitochondrion, but in the “soluble” portion of the cell. Synthesis of acetyl FAAE is constitutive; this enzyme is present regardless of the substrate in the growth medium. The synthesis of the butyryl-hexanoyl FAAE is induced by the presence of either of the substrates. The details of induction of the butyryl enzyme in acetate-grown cells, and the de-adaptation of cells grown in butyrate and transferred to acetate, are given. One mole of pyrophosphate is produced for each mole of CoA-SH reacting, (thus establishing the prevalence of the acyl-adenylate pathway in Chilomonas fatty acid activation.

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SYNOPSIS. The sterols of a number of protozoa grown in axenic culture have been examined. Ergosterol is present in Polytoma uvella, Astasia ocellata, Haematococcus pluvialis, Crithidia oncopelti, Prototheca zopfii, Chilomonas paramoecium and Trypanosoma mega, all grown on sterol-free media. Ergosterol is also present in the culture form of Trypanosoma rhodesiense and occurs together with cholesterol and an unidentified sterol in Peranema trichophorum grown in the presence of cholesterol. P. uvella, A. ocellata, H. pluvialis and C. oncopelti also contain a sterol which is either spinasterol or its isomer chondrillasterol. The main sterol of Ochromonas malhamensis is probably poriferasterol, which is also present in C. paramoecium. Cholesterol, probably from the environment, is the only sterol in the blood form of T. rhodesiense. Tetrahymena pyriformis and Hartmannella rhysodes do not synthesize sterols.

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Flagellates of different nutrition modes (hetero-, mixo-, osmo-, autotrophic) from batch cultures and natural freshwater samples were examined for abundance, cell size and biovolume changes after fixation and staining. The methods used were formaldehyde fixation and staining with 4,6-diamidino-2-phenylindole (DAPI) or fixation with Bouin's solution combined with a quantitative protargol stain (QPS). The values estimated with these protocols were compared to a live drop counting method and inspection of living organisms. Cell dimensions were measured with a semi-automatic image analysis system. We observed cultured species of Bodo saltans, Chilomonas paramaecium-group, Cryptomonas sp., Entosiphonomonas cf. sulcatum, Goniomonas cf. truncata and Paraphysomonas cf. vestita. Chemical treatment caused cell loss of up to 56%. In contrast lower abundance of field samples was determined via live counting than via formaldehyde and DAPI treatment. The number of living flagellates