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The fine structure of the opercula of Spirobis borealis Daudin and S. pusilloides Bush, and the primary and secondary operculum of S. granulatus (L) have been examined by electron microscopy. In different regions, the epithelium of the operculum exhibits variations in thickness and fine structure which correspond to transitions from peduncular to opercular wall to opercular plate epithelia. Externally, the peduncle and walls of the operculum are covered by a cuticle which is composed of several layers of fibrils/fibres embedded in an amorphous matrix. It is regularly traversed by microvilli from underlying cells. At the operculum rim, the cuticle changes so that its appearance is thick and solid. It continues across the roof of the operculum as a thin layer overlying a calcareous plate. The secondary operculum of S. granulatus differs from those of the other species in that an internal calcareous plate and solid cuticle line the roof of the operculum. It differs further in possessing an opercular pore. The possibilities are discussed of the cuticle fibrils/fibres of the peduncle and the opercular wall being collagenous in nature, and later being transformed to a solid tanned structure overlying a calcareous plate. The modes of secretion of the cuticle and calcareous plate by underlying cells are also discussed.

The effects of the implantation of 1-4 pairs of Corpora allata on the development of the eggs and the follicular epithelium ofCarausius morosus has been studied. The degree of the effects is determined by the number of the implantated C. allata. More than 3 pairs inhibit without exception any metamorphosis. All the eggs and their follicle epithelium of the giart larvae show defects of various kinds; especially of the egg shell. The development of the operculum and capitulum is independent of the development of the other parts of the shell. All deformities are explained by the disturbed proportion of Ecdyson and the hormone of the corpora allata. Normal development of the eggs requises the prior dissolution of the ventral glands of the head (=prothoracic glands).

Roman snails ( Helix pomatia ) have been treated with pp′ -DDT from 2 wk of age until hibernation. Taking snail size into account, relatively low doses of DDT significantly reduced shell and operculum weight whereas higher doses of DDT did not cause this response. After reemergence from hibernation, the incidence of operculum eating was significantly higher among snails hibernating late in the season, and as exposure to DDT increased so operculum eating became more prevalent. Shell thinning in snails due to pesticide is likely to have occurred in some heavily treated agricultural localities if the response of other species to DDT is similar to that of Helix pomatia .

SUMMARY The structure of the capsule of Urosalpinx is described and discussed in relation to the normal hatching process. Experiments have shown that development and the hatching process are inhibited at a temperature of 5°C, but only the egg stage is killed at this temperature. Normal hatching appears to result from the liberation of some enzyme-like substance which dissolves the cementing attachment of the operculum. It is suggested that capsules found ready to hatch before the normal spawning season were deposited at the beginning of the previous winter and have survived winter temperatures in a state of inhibited development.

When the adult functional operculum of the serpulid polychaete Hydroides dianthus is amputated at any level below the secondary cup, the rudimentary operculum develops into a functional one. Concomitantly a new rudimentary operculum regenerates from the stump of the former functional operculum. This reversal of asymmetry is proportional to the degree of injury (e.g., amputation > crushing > ligation > puncture). Amputating the rudimentary operculum does not affect the functional one, but in some cases the regenerating rudimentary operculum may differentiate into a second functional operculum. When distal portions of both opercula are removed, reversal occurs, and if the two opercula are amputated simultaneously at the base, a functional operculum regenerates on the side opposite its original position. If, however, the branchial apparatus is amputated together with both the functional and rudimentary opercula, the latter tends to regenerate on the original side. Thus the opercular regulatory system distinguishes between degrees and types of injury to the functional operculum, and the branchiae may be involved in opercular relationships. If the animal is decerebrated or the supraoesophageal ganglion is bisected, the opercula are still able to reverse normally. No reversal occurs when the external opercular nerves are severed, but in about one-third of the animals reversal occurred after section of the internal nerve. No direct nervous connection is involved in opercular communications, but the internal opercular nerve is implicated in stimulating reversal.

Summary. A study of the cranial anatomy of the entire head of Bufo melanostictus, Bufo parietalis, and Nectophryne misera, and the anterior region of the head of Bufo hololius and Bufo beddomii, reveals the following interesting facts:— 1 The anterior extension of the gl. nasalis medialis through the fenestra nasobasalis into the anterior region of the cranium, to occupy a position in between the gl. intermaxillaris, is noticed in B. melanostictus. The gl. nasalis medians do not penetrate through the fenestra naso-basalis in B. parietalis, B. hololius, B. beddomii, and N. misera. 2 The septomaxillary sends a limb into the plica in the region of the anterior nares in the Bufonid examples studied; the limb of the bone appears in the plica posterior to the anterior narial opening in N. misera. 3 The eminentia olfactoria is elevated in all the species of Bufo studied; the eminentia is not elevated in N. misera. 4 The sphenethmoid is bony in B. melanostictus, B. beddomii, and N. misera; in B. hololius it is cartilaginous, and in B. parietalis the bony sphenethmoid possesses cartilaginous areas. 5 The palatine is present in all the species of Bufo examined, while in N. misera it is absent. 6 The processus basalis is small in all the forms examined. It is merely a lateral extension of the oticus cartilage, and posterior to the oticus connection of the crista; the basal process also unites with the otic capsule to form a “pseudobasal” connection. 7 The frontoparietals have united mesially in N. misera; in the examined species of Bufo and in N. misera the fronto-parietals unite with the prootic bone. Posteriorly the prootic is indistinguishable from the exoccipital. 8 Of the plectral apparatus a large pars externa, a bony pars media, and a large pars interna are seen. A pars ascendens plectri—a commissural cartilage between pars externa and crista parotica—is noticed in all. 9 The operculum is sickle-shaped and depends from the otic capsule. 10 In N. misera the quadrate cartilage is feebly invaded by the quadrato- maxillary. 11 The complete absence of the “bursa angularis oris” of Fuchs (1931) (the “Mundwinkeldruse” of de Villiers) is noteworthy.

Taschenberg (1879) briefly described, under the name of Didymozoon scombri, a trematode which he recorded as occurring in pairs in cysts on the inside of the gill-covers of Scomber colias at Naples. Odhner (1907) found what he believed to be the same species not uncommonly in small specimens of S. scombrus off the west coast of Sweden, but was unable to find it in the larger fish taken in the early summer. He gives a minute description and excellent figures of the worm. Johnstone (1914) has also given a good, though diagrammatic, figure of its anatomy. Odhner describes the worm as occurring most commonly in paired cysts on the upper pharyngeal bones, but also in exceptional cases in cysts on the inside of the gill-covers and on the outside of the head, close behind the eye. About half the cysts examined by him contained two worms, the rest from three to seven. Johnstone describes the cysts as being most commonly situated ” “on the roof of the mouth beneath the pharyngo-branchials”, but also sometimes on the basi-branchials, on the external surfaces of other parts of the gill-bars, or on the internal surface of the operculum. One cyst contained as many as sixteen worms. According to Dollfus (1926), he and Monod found cysts containing one, two, three or more worms in the mucosa of the mouth, palate and gills of S. scombrus, and also single unencysted worms under the transparent skin behind the eye.Thus at least two authors record the same worm as occuring both inside the mouth and on th e outside of the head, behind the eye.

Movements of the lower jaw and operculum have been recorded simultaneously with the associated pressure changes in the buccal and opercular cavities during breathing of the following species: Trachurus trachurus (L.), Clupea harengus L., Gadus merlangus L., Onos mustela (L.), Crenilabrus melops (L.), Cottus bubalis Euphrasén, Blennius ocellaris L., Trigla gurnardus L., Callionymus lyra L., Pleuronectes platessa L., Microstomus kitt (Walbaum), Conger conger (L.), Syngnathus acus L. In all species ventilation of the gills is achieved by the action of a buccal pressure pump and of opercular suction pumps. The time course of the pressure changes indicates differences in the relative importance of the two pumps which are related to the habitat of the fish. The suction pump becomes of greatest importance in fishes which spend most of their fives on the sea bottom. In several species the differential pressure curve does not include the brief period of reversal in pressure gradient found in most fishes so far investigated. Notable among these species are the two flatfishes investigated and in which there is some evidence for an active opercular valve. In general, the results confirm the validity of Baglioni’s classification of the respiratory mechanisms of teleost fishes.

Opercula of Paleozoic gastropods are rarely found together in great numbers and may occur separated from their shells, making their identification with a particular species or genus uncertain. An unusually large collection of 27 opercula from one locality in the Lower Silurian (Llandoverian) of Quebec permits documentation of their variation and ontogeny. Comparisons of these opercula with previously reported specimens from Gotland indicate that the operculum of Oriostoma can be distinguished by its unique sculpture. The exterior surface of Oriostoma has counterclockwise multispiral coiling, whereas the interior has an opposing counterclockwise paucispiral coiling.

Enteromorpha lingulata J. Agardh (Chlorophyta) and Giffordia mitchellae (Harvey) Hamel (Phaeophyta) were found growing on opercula of Tilapia aurea (Steindachner) cultured in sea water. Fish observed had mild Vibrio and Aeromonas bacterial infections, manifested by abscesses on their opercula and other areas of the body. Algal growth was observed only on the operculum, which appears to be a more suitable attachment site due to its bony nature. Abscessed areas on opercula were devoid of scales. Mechanical abrasion resulting in scale loss appears to provide a suitable attachment site for algae. Plants examined were small, up to 6 mm in length. Tufts of algae covered opercular abscesses. Fish did not appear to be attracted to tufts of algae growing on other fish; all fish appeared normal in behavior, exhibiting a positive response to feeding and satisfactory growth.

When the Crouan brothers (1857, 1858) discovered the operculum at the top of the ascus, they placed all species with this structure in the genus Ascobolus Persoon ex Hooker. Boudier (1879, 1885) was the first to recognize the importance of the operculate mode of ascus dehiscence for the classification of the discomy-cetes. Accordingly, he divided the cup fungi on the basis of this character into two groups: the Operculatae and the Inoperculatae. It is a notable fact that none of Boudier’s contemporaries (e.g., Quelet, Karsten, Fuckel, De Notaris, Schroeter, Saccardo, Rehm, Cooke, Phillips, Lindau) accepted this division. It became accepted only much later by Gaumann (1926), Seaver (1927, 1928), Nannfeldt (1932), and Le Gal (1947, 1953). A subdivision of the cup fungi based on the mode of ascus dehiscence is now accepted by most mycologists.

A lymphosarcoma that appeared to be of thymic origin and of lymphoblastic type was found in a 3.5-yr-old Atlantic salmon (Salmo salar). The fish was from a population of 60 broodfish maintained at a research fish laboratory. A large tumor mass was found under the left operculum. Small tumor nodules were found on the swim bladder and in the abdominal adipose tissue. The location of this neoplasm differed from those of previously described tumors in this fish species.

Diastoma melanioides (Reeve 1849) is the sole survivor of a long lineage of gastropods in the genus Diastoma Deshayes 1850, family Diastomatidae, and is not well known in the literature. This group was common in the Tethys Sea during the Tertiary and was most abundant during the Eocene. The living species is confined to shallow-water habitats in southern Australia. The taxonomic assignment of the group and its relationship with other cerithiaceans was based on shell characters until recently, when I examined the soft parts of the one extant species. The operculum, radula, and internal anatomy provide the additional characters necessary for a proper assignment and allow a more informed judgment about the relationships of the diastomids to other cerithiaceans. A more detailed account about the anatomy and systematics of Diastoma may be found in Houbrick (1981:589–621).

The morphology of the opercularis system of anuran and caudate amphibians suggests that it acts to produce motion of the operculum that in turn produces fluid motion within the inner ear. The operculum and opercularis muscle form a lever system, with a narrow connection between the operculum and otic capsule acting as a fulcrum about which the operculum moves in response to forces applied via the muscle. The opercula of many species possess a muscular process on which the muscle inserts, thereby increasing the moment arm through which the muscle acts. The tonicity of the opercularis muscle allows tensile forces produced by substrate vibration or other mechanical energy applied to the forelimb to be effectively transmitted to the operculum; the elasticity of the connective tissue holding the operculum in place should act to return the operculum to its original position. The opercularis systems of frogs and non-plethodontid salamanders are similar structurally and functionally; that of plethodontid salamanders is structurally distinct but also functions as a lever system. Fluid motion produced by opercular motion could stimulate various end organs of the inner ear; the saccule, lagena, and amphibian papilla are in close approximation and wave energy could directly affect their otoconial or tectorial structures. In those anurans with a tympanic ear, the stapedial footplate and operculum articulate, but this articulation allows both to move independently. The stapes-tympanum complex and opercularis system therefore appear to be independent functional systems, and it is unlikely that the opercularis system modulates middle ear responsiveness. The general design of the opercularis system is consistent with a function in reception of substrate vibrations.

The first signs of sylvian depression in embryogenesis may be detected at the end of the 2nd intrauterine month and become more apparent as a sylvian groove at the end of the 3rd month. The temporal operculum grows more effectively in the anterior two-thirds and reaches the sylvian fissure in the 4th month. At the same time, the frontoparietal operculum becomes evident and gradually extends backward to meet the anterior part of the temporal operculum. These changes occur in the later half of the 5th month (2). As the growth energy of the temporal operculum is more intense than that of the frontoparietal, it follows that, when the opercula meet in the 6th intrauterine month, there is more of the sylvian area covered by the temporal than by the frontoparietal operculum.

SUMMARYA synthetic lethal system involving homozygous combination of the non-allelic eye mutantseye-goneandeyelessis described. The major lethal crisis is towards the end of the pupal instar although a number of double homozygotes die at pupation. The pupal lethal crisis can be overcome in a number of individuals by the experimental removal of the operculum from differentiated pupae. However, only a few of the resulting enclosed double homozygotes proved fully viable, the remainder dying almost immediately after emergence. Dissection of the surviving adults revealed that the brain is located in the anterior thorax.

The surface morphology of metacercariae isolated from Puntius spp., adult worms from infected hamsters and eggs of Centrocestus formosanus (Digenea: Heterophyidae) were studied using scanning electron microscopy. It was found that the surfaces of the metacercariae and adult worms were closely similar in appearance. The oral sucker was surrounded by a circumoral expansion with two rows of 32 spines (16 spines each). The ventral sucker, with six large nonciliated papillae on the lip, and the genital opening were located midventrally. The excretory pore was terminal. The body surface was covered with pectinate scale-like spines of varying sizes. The scales in the middle area were larger than those in the anterior and posterior parts of the body. Sensory papillae, mostly uniciliated, were present in greater abundance at the anterior region of both stages. However, morphological variations were observed among the adults depending on the age of the worms. At 4 weeks, the oral sucker and circumoral expansion were cobblestone-like in structure and the grooves of spines split compared with their smooth surfaces at 10 days. In addition, the ventral sucker became depressed and its large papillae on the lip disappeared at 10 weeks post infection. Multiciliated papillae were also present in 10-week old worms. Each egg of this parasite possessed a prominent operculum and a latticed design on the egg shell.

The intertidal gastropod, Cerithidea obtusa were obtained from Bako and Sematan (Sarawak) and Deralik (Perak) in February and December 2006. Besides the shells, the snails were dissected into six different soft tissues. The soft tissues and the shell were used for detection of heavy metals. It was found that the highest concentrations of Cu (112 - 178 I¼g/g dw) and Zn (117 – 161 I¼g/g dw) were found in the tentacle; the highest concentrations of Cd (4.41 - 5.37 µg/g dw), Pb (53.2 – 63.8 µg/g dw) and Ni (26.1 - 27.9 µg/g dw) were found in the shell. On the other hand, the highest Fe concentrations (910 - 2921 µg/g dw) were found in the operculum. The cluster analysis revealed that the accumulation of heavy metals were clustered into a few groups, where metals were found in the shell are significantly different from the other soft tissues. The multivariate statistical analyses revealed that the accumulation by the different parts were inter-related with one another. Based on the multiple linear stepwise regression analysis, it was also found that the caecum was the most influential organ in accumulation of the studied heavy metals in the total soft tissues. The results indicate the ability of C. obtusa to accumulate heavy metals in the different tissues, hence fulfilling the important criteria as a good biomonitor.

A human case of Echinostoma cinetorchis infection was found in Seoul Paik Hospital on August 1987. Large trematode eggs, 98.9 x 62.7 micro-m in average size, were detected in stool examination. The eggs had a small-sized operculum and abopercular wrinkling. After treatment with praziquantel(single dose of 16.2 mg/kg) and purgation with magnesium citrate, an adult fluke was collected. It was 8.0 mm long, equipped with 37 collar spines around head crown, and had only one testis just behind the Mehlis' gland. It was identified as E. cinetorchis Ando et Ozaki, 1923. The patient is an 18-year old man residing in Seoul, and was hospitalized due to nephritis. He had eaten raw meat juice of fresh water fishes such as top minnows(Oryzias latipes) and loaches, or tadpoles, which are considered possible souce of this fluke infection. This is the 4th human case of E. cinetorchis infection in Korea.

The development of 8 eggs of Triatoma sordida (Hemiptera: Reduviidae) was studied during November and December 1979 in Paraguay. The events of development at a mean temperature of 26 °C included the first appearance of eyespots (days 6–7); the change in position of the embryo and the appearance of a dent in the egg (days 7–9); darkening of the operculum (days 9–10); completion of the darkening of the eyes (days 12–14); and hatching (day 17).

Scanning electron microscope studies have been conducted on the operculum of sporangia of Trichia crateriformis and its structure has been compared with that of other operculate Myxomycetes. The operculum of T. crateriformis consists of a single layer of sporelike bodies that have cell walls ornamented with warty excresences similar to those of the spores. It adjoins the membranous peridium of the sporangium in a transition region which constitutes the dehiscence zone. In other taxa with operculate sporophores examined the operculum is membranous and has a structure generally similar to that of its associated peridium. The type of operculum in T. crateriformis may be unique for the Myxomycetes. Several species of Myxomycetes form sporangia furnished with a well-defined operculum. Species exhibiting this characteristic are Metatrichia vesparium (Batsch) Nann-Brem., certain species of Craterium and Licea, Perichaena depressa Libert, and Trichia crateriformis Martin. During the course of some scanning electron microscope (SEM) studies of types of authenticated specimens of taxa in the Trichiaceae, we observed that the operculum of the sporangium of T. crateriformis is strikingly different in structure from that of its contiguous peridial wall. The T. crateriformis operculum was noted to consist of discrete spore-like units with ornamented wall surfaces similar to those of the spores. A report on this apparently unique type of operculum structure is presented in this communication.

Derocheilocaris remanei katesae was described from Durban on the east coast of South Africa by Noodt (1954). He distinguished this subspecies on the basis of the shape of the anterior portion of the cephalon, the spines and seta of the anal operculum and the body shape. The work of Hessler ( 1972 ) on African mystacoca rids brought to light the extreme conservativeness of this subclass and the minute nature of differences sufficient to warrant species status. Forms from Angola and South West Africa, considered by Noodt to be D. remanei, were shown by Hessler to be distinct species and named D. angolensis and D. delamarei respectively. D. r. katesae thus became separated from the type D. remanei by at least two species and nearly 1000 km of coastline. A further species was then recorded from Algoa Bay on the south-eastern corner of Africa (McLachlan & Grindley, 1974) and named D. algoensis. At the time it was not certain whether D. r. katesae and D. algoensis were the same species or whether D. r. katesae was distinct and warranted species status. Noodt's (1954) description of D. r. katesae was not sufficiently detailed to decide this. Now as the result of a series of collections along the east coast of South Africa both north and south of Durban it is possible to clarify this. All specimens examined from these east coast collections are identical to D. algoensis. Three points of difference between Noodt's (1954) description and D. algoensis, namely (1) the antero-medial notch of antennulary portion of cephalon, (2) the constriction separating antennulary portion of cephalon from the rest of the cephalon and (3) the acute process on the supra anal process (anal operculum), were checked. In all cases these appeared as described for D. algoensis, namely (1) a U-shaped anteromedial notch in the cephalon, (2) the constriction in the cephalon had a distinct notch and (3) the supra anal process had two acute processes, a short stout vertral one and a slender, longer dorsal one. It must thus be concluded that D. r. katesae and D. algoensis are conspecific and the small differences in Noodt's description were due to distorted specimens. It is therefore suggested that D. r. katesae Noodt, 1954 be considered a senior synonym of D. algoensis McLachlan & Grindley, 1974. The recorded range of D. katesae is now extended from Algoa Bay up the east coast of South Africa to Sordwana Bay near the Mozambique border. REFERENCES

Adult and juvenile Lymnea peregra (0. F. Muller) were in laboratory experiments found to be more tolerant to high temperatures (36 and 38?C) than adult and juvenile Theodoxus fluviatilis (L.). This difference was also indicated by the field distributions of the two species. Seasonal differences were found in the tolerance of both species. During the egg laying phase, the heat tolerance of L. peregra dropped drastically. Adult T. fluviatilis was more tolerant to desiccation than adult L. peregra. This resistance is probably due to the existence of an operculum in T. fluviatilis and to the found behavioural differences at low humidities. Juvenile T. fluviatilis in egg capsules, however, are less tolerant to desiccation than are juvenile L. peregra. This is compensated for by T. fluviatilis deposing the capsules deeper below the water surface.

Eggs of Cuterebrinae have been described by Hadwen (1915), Townsend (1915), Parker and Wells (1919), Ferris (1920), Bennett (1955), and Haas and Dicke (1958), but no case of oviposition has been observed in nature. Townsend (1915) and Dalmat (1943) suggested that the eggs are probably deposited in burrows or runways of rodents. Parker and Wells (1919) observed in their study of Cuterebra tenebrosa Coq. that eggs were "glued to the side of the box in which they were laid". Eggs were observed to be fastened by the groove on the ventral surface of the egg. Sillman (1956), and Ryckman and Lindt (1954) observed egg laying in the laboratory. They found that the female fly extended its ovipositor and deposited eggs as it walked about on blotting paper. Sillman (1956) found that eggs were generally deposited singly in long rows. Painter (1930) observed Bogeria baccata Fab. ovipositing on grasses. Bennett (1955) reported that eggs are fully developed early in the life of the adult fly, for the life span of the adult is short and ovipositing commences within one or two days after the adult has emerged from the pupa. Townsend (1915) observed that force was required to remove the operculum from dried eggs but the application of saliva "caused the appearance of an outlining darkened band around the margin of the cap". Sillman and Smith (1959) observed that larvae were stimulated by moist environments, for when larva were placed in the mouth of Peromyscus leucopus they moved "out of sight along the side of the tongue towards the back of the throat". Leonard (1933) was the first to suggest that oviposition might be direct, with female flies being attracted by the moist nipples of female rabbits. Collections of rodents from Ontario, Canada, completed prior to this study indicated that oviposition may occur directly on the hair of Tamias striatus as Leonard (1933) suggested.

(1) The asymmetrical development in Hydroides opercula is due to the growth difference between two sides in the same kind of organs. The presence of a functional organ holds its mate in check. Therefore, taking off the functional operculum results in the development of the rudimentary side. (2) This phenomenon of compensatory regulation cannot be considered to be brought about by a nervous reflex set in motion by the stimulation of damaged nerves in the operated operculum, since, for example, the inhibitory influence to a certain extent depends on the degrees of injury. (3) It is also not proved to be due to the production of a certain chemical substance which stimulates the rudimentary organ to grow, while the wound itself affects directly the inhibitory action of the functional operculum. (4) The inhibitory influence is only localized in the operculum and not outside of it. Therefore, cutting off the gill filaments or other parts of the body does not bring a reversal of asymmetry. (5) Within the limit of the operculum there is no special centre of the inhibitory influence, which depends on the intactness of the internal constitution of the organ. Those peripheral parts outside the limit of direct blood supply can be cut off, without the resulting reversal of asymmetry. A simple puncturing with a fine needle also has no effect. But greater injury accompanied by an outflow of blood always starts the rudimentary organ developing. (6) The functional operculurn has no regenerative capacity, while the rudimentary one still has. The injured operculum is thrown off sooner or later from the body, and a new start repeats from the beginning the original development. By accelerating this regenerative development of the old functional organ, or properly controlling the growth of the rudimentary organ on the opposite side, a symmetrical animal with two large opercula can easily be derived. On the other hand, if both rudiments antagonistically check each other's development, a symmetrical animal with two small rudimentary opercula is produced. (7) Since, however, either the right or the left or even both rudiments can be made to develop into a functional organ, the inhibitory influence must act at first on both alike, unless a threshold value is assumed. In the present species of Polychsete it is as a rule the right-handed one that grows more quickly than the other. (8) With regard to the nature of the asymmetry in Hydroides it seems to be quite different from that in the male Gelasimus in which the asymmetry of the chelas is said to be derived from the symmetrical condition relatively late in development, and the relation, once attained, becomes fixed. (9) In Hydroides norvegica at least, the opercula show a tendency to right-handed growth from the beginning of their development, but this condition of asymmetry is very unstable and is easily reversible by an external influence even in the adult state, i.e. there is no critical stage at which it is irreversibly determined.

A new species, Demodex gapperi, is described with notes on its biology and host relations. Y-shaped ova, larvae with dorsal fingers and long legs III, prominent legs in nymphal and adult stages, are noted as adaptations for survival in an unusual habitat, the ducts of the Meibomian glands. The mites consume cells of the duct epithelium. An incidence of 56.3% is reported, with a 70% incidence in male and 40% in female host animals. Population studies indicate a sex ratio in the mites of 1:2 and a maximum of 73 mites from one host animal. This new species was discovered in our laboratory in 1962; however, adequate specimens for accurate description have just recently become available. Since in many respects this is a unique demodicid, the description will be followed by some account of the biology of the mite and of its host relationships. One aspect of this last, the Y-shaped ovum, has already received some attention (Nutting et al., 1968). MATERIALS AND METHODS Eighty red-backed voles (27 females, 53 males) were examined for demodicids. Scrapings from 20 of these (10 females, 10 males) were examined, each for 6 body areas (eyelid, dorsal, ventral, genital, muzzle, and perianal). For the other voles, skin scrapings were examined for dorsal and eyelid areas or eyelid only. All scrapings were mounted in Hoyer's medium or examined in peanut oil or physiological saline. In a few cases complete eyelids were digested in 10% KOH, washed, centrifuged, and examined to obtain population counts. Sectors of skin from the 6 body areas, above, and from heavily parasitized animals were fixed in Bouin's solution, paraffin-embedded, cut at 8 to 10 Au and stained with hematoxylin and eosin or Mallory's triple stain. All measurements are in microns, and are given in Table I. Received for publication 8 September 1970. *Zoology Department, University of Massachusetts, Amherst, Mass. t Study supported in part by a National Science Foundation Grant GB-3516 to the senior author. $ University of Nigeria, Nsukku, Nigeria. ? Wisconsin Alumni Research Foundation, Madison, Wisconsin. Demodex gapperi sp. n. (Figs. 1-13) Description: with characters of the genus One of the largest members of the genus; one female measured 409.6. Striking sexual dimorphism, with males approximately two-thirds length of females-especially noticeable in opisthosomal length (avg male 164.3 vs. female 252.6). Males (Fig. 1): Gnathosoma slightly wider than long. Supracoxal spines (Fig. 8) small, peglike, directed anterolaterad. Pharyngeal bulb oval with subgnathosomal setae anterior (Fig. 9). Podosoma somewhat oval in outline, less than one-third total length, and wider than opisthosoma. Legs long, evenly spaced, and approximately one-half each visible from dorsal aspect. Opisthosoma over onehalf total length, gradually tapering posteriorly with rounded terminus. Opisthosomal annuli narrow, very faint anteriorly but well-marked posteriorly. Genital orifice (Fig. 10) directly over midline between legs I and II, ovoid with distinct operculum. Penis sheathed, 20.1 long, curving ventroposteriorly and with bulbous base. Anterior dorsal tubercles above and slightly anterior to legs I. Posterior tubercles in line with anterior tubercles, at mid-line of podosoma. Females (Fig. 2): Gnathosoma and supracoxal spines similar to male but slightly larger. Pharyngeal bulb and subgnathosomal setae as in male. Podosoma elongate-oval, approximately one-quarter total length, wider than opisthosoma. Legs shorter than male, evenly spaced. Opisthosoma similar to male but markedly longer. Annuli also similar but more pronounced. Vulva 22.4 long, irregular slit, opening on opisthosoma (Fig. 11) behind closed, fused epimeral plates. Ova (Fig. 3): Remarkably long (295.8), Yshaped, widest (29.9) at base between anterior prongs. Larvae (Fig. 4): Very slender, elongate. Legs I FIGURES 1-7. Anatomy of Demodex gapperi. 1. Dorsal view of male. Arrow indicates penis. X 270. 2. Ventral view of female. Arrow indicates vulva. X 270. 3. Ovum. X 270. 4. Dorsal view of larva. Arrow indicates dorsal finger. X 270. 5. Lateral view of larva, showing dorsal finger (left) and legs I, II, and III. X 270. 6. Ventral view of nymph. X 270. 7. Anterior prongs of ovum showing larval gnathosoma (arrow) in one prong. X 1,000.

THE nature of the changes of hydrostatic pressure produced in the buccal and opercular cavities by the breathing movements of teleost fishes has been discussed by several workers1–3. Pressure measurements were made by Woskoboinikoff and Balabai4, but their results give no indication of the time-course of these changes. Using a capacitance manometer, we have been able to measure pressure changes in both buccal and opercular cavities throughout the complete respiratory cycle in three species of freshwater fish. Cine films taken simultaneously made it possible to plot the movements of the mouth and operculum without loading these structures in any way. The action of the mouth and opercular valves was also studied from the films.

The infection with tapeworm of the Mesocestodes sp. has been rarely reported and only 8 cases of human infection were found in the world up to date. This is to report the first case of human infection with this tapeworm belonged to Cyclophyllidea in Korea. In January 1967, a 45 years old man visited to the out clinic of St. Mary's Hospital with the complaints of intermittent indigestion and abdominal distension nearly for 1 year. Laboratory findings appeared almost normal except increased eosinophils up to 14 per cent. The characteristic ova of Mesocestoides sp. were found by the serial stool examinations, which contained hexacanth larva inside the egg shell without operculum as in Cyclophyllidea. It was failed to reveal the scolex by the first evacuation, but one among 3 worms evacuated by the treatment with atabrine and enough purgations 2 months later, has been found the characteristic scolex. They were 85 cm to 136 cm long and the scolex had 4 distinct suckers but no rostellum, the matured proglottid had numerous testes bilaterally and ovary with yolk glands in central parts, and in the gravid proglottid spiral uterus was opened to uterine pore and characterized by the spherically distended uterine capsules. The patient had the history of ingestion of 15 snakes as raw about 1 year ago as usually seen in Japanese cases.

THE spotted swamp tree frog, Pseudacris clarkii (Baird), ranging from eastern Texas to southern Kansas, has been treated generally as a subspecies of the swamp tree frog, P. nigrita, and is so listed in the fifth edition (1943) of Stejneger and Barbour's Checklist. Smith (1947) found breeding populations of P. n. triseriata and P. clarkii in the same ponds, but without mixing, in areas of overlap in Texas. He inferred that clarkii is a distinct species, and has discussed the differences. Youngstrom and Smith (1936) described the tadpoles of P. n. triseriata, as Green (1938) has done for P. brachyphona. Descriptions of eggs and tadpoles of some other forms of Pseudacris are presented by the Wrights (1929, 1931, 1942). We collected eggs and adults of P. clarkii near Hackney, Cowley County, Kansas, April 26, 1948, in a temporary rain pool. The egg masses were conspicuous and abundant, attached to dead weed stems as shown in Wright's Handbook (1942: 110). By following the development of the more recently laid eggs we obtained an approximate chronology of the embryonic and early larval stages, up to the attainment of definitive tadpole characters. Comparison with numbered stages of Rana pipiens (Shumway, 1942; Rugh, 1948) shows that development of P. clarkii up to the time of hatching goes at approximately the same rate, but the change to an active tadpole is then completed more rapidly. For example, the gills had become internal and the operculum was complete at about 41/2 days from the presumed time of fertilization in clarkii instead of 71/2 days (pipiens) at 25? C. The growth of the tadpole, however, is much more rapid in Rana, for a considerably larger size is reached before metamorphosis. Another point of interest is the failure of the external gills in P. clarkii to become slender and functional. They are covered by the operculum while still in a rudimentary form (Fig. 16). This abbreviation of a step in larval development may be correlated with the reduced size of Pseudacris embryos, which are perhaps small enough to permit adequate respiration through the body surface alone. The changing features of early stages may now be summarized: 24-36 hours (Figs. 1 and 2). Gastrula and yolk-plug. Average vertical diameter of 16 gastrulae 1.28 mm., extremes 1.0-1.66 mm. (measured in life by ocular micrometer). Color pale brown, not heavily pigmented, which would be an advantage in experimental embryology, although the small size is a handicap in manipulation. Wright (1942) gives "citrine drab and ivory yellow" for the animal and vegetal poles, respectively, of the eggs.