Search

The behavior of Cura foremanii and Dugesia tigrina in large and small spaces was examined. It was found that the smaller the space (the greater the probability of contact with a corner for rectangular spaces and the greater the degree of angularity for cylindrical spaces), the shorter the mean time to cessation of locomotion. When given a choice between settling in a large or a small volume under diurnal conditions, both C. foremanii and D. tigrina chose the small volume. With continuous darkness, while D. tigrina appeared to continue to choose the smaller volume, C. foremanii avoided it. The behavior was explained as an interaction of taxes.

The Best & Rubenstein study was replicated with a control for handling with the planarian Cura foremanii. There were no signicant differences between the mean feeding latencies of the Control, Handled, and Familiarized groups. Additional studies revealed that food size affected the frequency of C. foremanii eaitng (but not D. tigrina) but not feeding latency and that prior handling decreased the feeding latency for Dugesia tigrina. It was concluded that failure to replicate may indicate that C. foremanii, particularly in light of its normal habitat, may not be as reliable a laboratory animal as D. tigrina.

In the present investigation aggregations developed in shadow under heterogeneous illumination conditions, on a black surface under homogenous illumination conditions, and differentially according to species under heterogeneous illumination conditions in which the white background was in shadow and the black background was directly illuminated. For this latter effect, D. tigrina aggregated in shadow while C. foremani aggregated in both shadow and black background. Introducing new planaria to bowls containing aggregations and a newly introduced shadow resulted in the establishment of new aggregations under shadow, while introducing planaria to bowls containing aggregations and newly introduced black tape resulted in new planaria joining established aggregations. Finally, introducing new planaria to bowls containing aggregations established on black tape and a newly introduced shadow resulted in C. foremani consistently joining existing aggregations while D. tigrina did not show such a preference, establishing aggregations under shadow as well. These findings were interpreted as providing support for the chemotaxis, distinctive morphology, and photokinesis hypotheses of aggregation formation in planaria. Specifically, aggregation formation, mediated by visual and chemical sensory processes, is usually the result of the joint effects of chemotaxis, distinctive morphology, and photokinesis.

In 1899 Hallez (4) made the generalisation that the most important difference between the regeneration in Triclad and Polyclad Planarians was to be found in the fact that fragments of the former could regenerate in the absence of the central nervous system, whilst in the latter some portion of the cerebral ganglia must be present in order for regeneration to take place. Child (1) has confirmed the fact that the presence of cerebral ganglia, or at least intact nerve roots, is necessary for regeneration of the anterior end and sense organs of Polyclads. The experimental work by the same and other authors has also established that, among Triclads, the genus Planaria is able to regenerate completely in the absence of cerebral ganglia. The following notes, however, show that in another Triclad genus, namely, Gunda , anterior regeneration is, as in Polyclads, dependent on the presence of the central nervous system. The experiments described below were carried out in the Plymouth Laboratory of the Marine Biological Association during the spring of 1913. I am greatly indebted to the director and staff of the laboratory for constant kindness during the course of my work at Plymouth. I also stand under obligations to the Royal Society, the Zoological Society, and the University of Cambridge for the use of their tables at the Plymouth Laboratory.

Since the description by Pallas in 1774 of their remarkable capacity for regeneration the planarians have been of interest to the biologist (cf. Brondsted9s excellent review—Brondsted, 1955). Dubois (1949) has shown that regeneration in planaria is due to undifferentiated totipotential cells referred to as neoblasts, which are the only cells known to divide mitotically. When the animal is cut or similarly injured, some neoblasts in the region of the wound rapidly differentiate to form a new epidermis, while other neoblasts divide and migrate towards the wound surface where they continue to divide and/or differentiate into various cell types. The finding of spontaneous growths or tumours in this simple material (Goldsmith, 1939) suggests that it may be of interest to study the nature of such tumours. Material for the present studies includes the species Dugesia etrusca and D. ilvana obtained from the laboratory of Professor Mario Benazzi of the University of Pisa, Italy.

1. Planarie lata possesses a short posterior zooid and undergoes fission. Fission does not interfere with sexual maturity, probably because the level of fission is far posterior to the genital pore.2. Susceptibility decreases from the anterior to the posterior end of the first zooid and increases again with approach to the posterior zooid.3. Head frequency varies in relation to level of body in the same way as susceptibility. The differences in head frequency at different levels increase as length of piece decreases, and head frequency is slightly lower in young than in old animals.4. Isolation of pieces is followed immediately by a great increase in susceptibility, CO2 production, and oxygen consumption, then a gradual decrease occurs during 12-24 hours to a level still far above that of whole animals. Later a gradual increase coincides with the progress of reconstitution.5. The increase in susceptibility after section in relation to body level and length of piece varies inversely as the susceptibility g...

performed with extracts of the comparatively closely related schistosomes of animals?-e.g., Schistosomum spindalis} Later, extracts of certain distomes? Fasciola hepatica2 and Eurytrema coelomaticumz of cattle?also were reported to serve as sources of antigen for immunological tests in human schistosomiasis. It appears from these studies that antigens common with some of those in the schistosomes of man are probably fairly widely dispersed among trematode worms, although there are

n/a

The physiological investigation of invertebrates is important for the study of the evolution of functions, and also for understanding the laws of interaction of functions and living structures in an elementary form. Flatworms (planaria) attract special attention because of the simple organization of their nervous system, which at the same time possesses the basic features of a centralized system in the form of cephalization and synaptic transmission.

The tropistic reactions of three Planarian species occurring in Cardiganshire streams, Planaria albissima , a common and generally distributed type, and Pl. alpina and Polycelis cornuta two Ice Age relicts whose occurrence is almost entirely limited to the neighbourhood of springs, have been studied with a view to determining their ecological significance (if any). All three species give the responses characteristic of the whole group of Triciadida (as established by previous workers) to light-, contact-, and chemical-stimuli: they differ to a considerable extent in their reactions to a current of water, Pl. albissima giving the characteristic positive reaction to a strong current, negative to a weak one, while the two glacial relicts exhibit a strong and constant negative rheotropism. These two species also show far greater sensibility to extremes of temperature than does Pl. albissima , as well as a more delicate perception of certain chemical stimuli. Their tropisms, as a whole, are in logical agreement with the facts of their occurrence only in environments of a very definite type, and with a partial seasonal migration (down-stream in winter, up-stream in summer) which has been found to occur in the streams of this district (Carpenter 1928).

1. Planaria, Dugesia dorotocephala, were starved for periods of 5-30 days, the heads and tails removed and the remainders of the worms were cut into three, four or six pieces. These sections were allowed to regenerate in tap water or in solutions containing yeast sodium ribonucleate (0.005-0.01%) horse serum (5%), amino acids (1%), and chick embryo extract (1%). The media were changed every second day. The cultures were observed daily and the time of eyespot formation was recorded.2. All of the nutrient solutions tested were effective in promoting the rate of regeneration of eyespots, particularly in the posterior pieces in which eyespots appeared 1-2 days sooner than in the tap water controls. The effect of the test solutions upon the extent of eyespot regeneration is less consistent, but some stimulation of differentiation at the posterior levels was observed.3. Exposure to yeast sodium ribonucleate for only a day after cutting the worms also stimulated head frequency posteriorly, but this is not as eff...

n/a

IN a paper on Planawia viaculala, published in i89S, Morgan called attention to an important feature of the regeneration of the pharynx, namely, that in regenerating pieces which were cut anterior to the old pharynx, the new pharynx forms "at the edge of the old tissue, but lying for the most part within the neew material," while if the cut were made posterior to the pharynx the new organ forms in the anterior end of the old tissue. During the next two years there appeared a number of papers describing experiments on the power of regeneration in planarians, but giving no further knowledge of the development of the pharynx except that to be derived from general statements of the various positions it may assume in the regeneratinog pieces. More recently a paper by Bardeen on the physiology of Planar/ia MaCu1/alt has taken up the formation of the pharynx in this species and given a somewhat detailed account of it. In studying the origin and growth of the new pharynx, I wished to find out if there were any marked difference between its formation in the new tissue of the anterior piece and in the old tissue of the posterior piece, since the conditions for regeneration seemed so unlike in the two cases. At the same time I was interested in observing in the posterior pieces what might be the influence of the reproductive organs when present in the region where we should expect the pharynx to appear, and if, under these conditions, the already existing cavities and external oipeningcan be made use of. In this connection I examined series of regenerating posterior pieces in which the cut had been made (i) just posterior to the pharynx, but at a time of year when the reproductive organs have disappeared; (2) anterior to these organs when they are fully developed; and (3) posterior to them. 633

1. Previous experiments (Allee, 1928, 1929) concerning the action of hypotonic water extracts of other Procerodes and Planaria maculata culture water on the marine Procerodes wheatlandi isolated therein, are confirmed. 2. Adsorption on charcoal or on egg albumen does not significantly affect the protection furnished by planarian culture medium. 3. No protection is furnished by egg albumen, gum arabic, or mucus made by dissolving dried parotid gland in water. Previous work had shown the same situation with gelatine. 4. Ethyl urethane, a depressant, does not give protection; it acts in this respect as had ethyl alcohol in previous experiments. 5. Water solutions or suspensions made from ether-soluble and ether-insoluble fractions of Procerodes extracts exhibit less protection than does the whole water extract. 6. Cane-sugar solutions definitely confer protection in all concentrations tried from M/1 to M/33⅓. Solutions of M/40 and M/50 gave the same survival as did the non-sugar controls. The protection conf...

One hundred-twenty planaria were randomly divided into 12 equal groups. The experimental groups were given 0, 150, 300, and 450 trials of paired light and shock. The light control groups were given 0, 150, 300, and 450 trials of light. The pseudoconditioning groups were given 0, 150, 300, and 450 trials of unpaired light and shock. After their respective training procedures, all groups were given 25 extinction trials on 4 successive days. Analysis revealed that there was no significant difference among the groups.

This paper reports observations on the number of neoblasts in diploid and triploid planarian biotypes, the relation of this number to the size of the animal and the distribution of neoblasts with respect to the long axis of the animal. The number of neoblasts is a function of animal length for both diploid and triploid biotypes, but no significant difference was found between the biotypes. The combined data yield a regression equation of log. (number of neoblasts) = 1·90 log. (length) + 3·47. The distribution of neoblasts with respect to the long axis of the planarian was found to have two relative maxima, one anterior and one posterior to the intercalary minimum associated with the pharyngeal region of the animal. The relative position of the pharynx remains unchanged with growth in the triploid animal, in contradistinction to the progressive shift cephalad in the diploid. As statistical analysis showed no significant difference in the effects of the histological methods employed on the two biotypes, this observation is interpreted as a demonstration of different modes of growth in the diploid and the triploid. The volume of the planarian (in the fixed state) was correlated with the animal’s length (when alive) to yield a regression equation of log. (volume) = 2·62 log. (length) + 5·70. The slope of this regression equation is highly significantly different from that of the neoblast regression line. Thus larger animals have a lower density of neoblasts, although more of them. It is suggested that this latter observation may have some bearing on the problem of senescence in planarians. Counts of objects in serial sections are subject to an overestimate which can be corrected by the method of Abercrombie. This method, however, is based on an assumption which is not always valid. Therefore a more rigorous correction formula has been derived. This formula was then applied to the measurement of neoblast nuclear diameters (in the fixed state). No significant difference was found for nuclear diameters of diploid and triploid neoblasts.

1. There is a decrease in the rate of locomotion of planarians after treatment with solutions of adrenin, followed by a return to the normal rate when the animals are again placed in water.2. In those individuals which have not been subjected to the influence of the extract more than an hour, this decrease in the rate of locomotion seems to be due rather to an increased excitability and lack of coordinated movement than to a slowing of the rate of muscular contraction.3. Planarians exposed to the action of adrenin for a longer period do not give evidence of extreme excitability, but seem to show a real decline in activity, which may be a secondary effect following the initial excitation.4. Those planarians whose initial rate indicates a state of depression travel more rapidly after treatment with adrenin. This would seem to confirm the suggestion that the effect of this extract upon planarian muscle is predominantly excitatory.5. Although no definite statement can be made concerning the effects of adrenal...

IT has been shown that temperature has a marked effect on the regeneration of Planaria torva. Lillie and Knowlton (2) have proved by experiment that the optimum temperature at which regeneration is completed is 29?.7 C.; the minimum, about 3? C. During the last month I have made a series of experiments on Hydra viridis and Hydra grisea, in order to test the effect of temperature on the regeneration of the hypostome and tentacles. A transverse cut was made through the reproductive zone of the polyp just posterior to the ring of tentacles. The body thus deprived of hypostome and tentacles was subjected to a gradual rise of temperature. The dishes in which the Hydras were placed after the operation were partially submerged in a water bath in which the temperature varied from 26? to 320 C. Readings were taken during the day at intervals of four to six hours; the variation was never greater than five degrees. Control experiments were made at room temperature, which ranged between I8? and 24? C. Observations were made at intervals of twelve to twenty-four hours, and regeneration was considered complete when the new hypostome and tentacles had attained their normal size.

SummaryThe planarian lends itself to parallel cellular and whole animal studies because it contains a single, morphologically identifiable population of toti-potential stem cells, without which the animal cannot long survive.Two genera, including five species and three auto- or allopolyploid biotypes, of planarian have been chosen for a study of the cellular basis of radiation lethality. The distribution of mortality times was found to be uni-modal and the x-ray dose–response curve, sigmoid. By the use of antibiotics, infection by commensal organisms was shown not to be a significant factor in mortality. The effects of several other treatments are interpreted in terms of altered metabolic rate. It is suggested that planarian radiation mortality is the end-result of a loss of reproductively-intact stem cells leading to insufficient replacement of worn parts of vital tissues.

In Nereis virens the rate of carbon dioxide discharge for the whole worm is roughly o ·01 milligram of gas per gram of worm per minute. In similar terms the rate for the mid-trunk is a little over 0 ·01 milligrams and that for the head and tail regions about half of this rate. In Planaria maculata large worms (87 mgm.) show a lower rate of carbon dioxide discharge (0 ·0050 mgm. per gram of worm per minute) than small ones (55 mgm.) (0 ·0069 mgm. per gram of worm per minute). Also normal worms have a lower rate (0 ·0050 mgm.) than cut worms (0 ·0063 mgm.). Planarians cut transversely into halves, quarters or sixths show in such fragments so uniform a rate of carbon dioxide discharge that there is no reason to believe that the rate is really different in different parts. In the actinians Sagartia luciae and Metridium marginatum the rate of discharge of the oral halves is indistinguishable from that of the aboral halves and these two rates are very close to the rates of the animals as wholes. These results point to the absence of the assumed metabolic gradients in Nereis, Planaria and the actinians. Hyman’s results on annelids with the susceptibility method were obtained on Nereis but are believed to be due to differential penetration and are not accepted as a proof of a metabolic gradient. Hyman and Galigher’s results on annelids involve a misuse of the Winkler method. Shearer’s results on earthworms apply only to the head and tail ends and should have been supplemented, to be conclusive, with determinations for the mid-trunk. Metabolic gradients if present are not factors in morphogenesis but are at best measures of activity which may serve as features in the description of organisms.

1. The young of Planaria dorotocephala produced by simple fission were found to consume 15 to 55 per cent. more oxygen than large worms, the difference depending upon the length of time which had elapsed between the last feeding and the time of testing.2. The young of Planaria velata, produced by an asexual process involving regeneration and a high degree of reorganization of the body, consume about 100 per cent. more oxygen than the worms from which they come. The greater difference in this species is undoubtedly associated with the method by which the young are produced.3. The sexually produced young of Planaria maculata consume about 50 per cent. more oxygen than the sexually mature worms. There is thus no significant difference between sexual and asexual young, when the latter arise by ordinary simple fission.4. This result, that young worms have a higher metabolic rate than old ones, is in accord with a considerable body of literature on other forms leading to the same conclusion; and confirms the wo...