38 INANITION AND MALNUTRITION 



ever undergoes marked changes, the earlier stages of which were described by 

 Greenwood ('88), as above mentioned. In contrast with the ectoderm, these 

 entodermal cells become less vacuolated by disappearance of the food- vacuoles. 

 Later the cells fuse into a syncytium, containing pigment, vacuoles and other 

 inclusions (Fig. n). The entoderm cells of the foot become indistinguishable 

 from the intestinal epithelium. The entodermal nuclei at first become some- 

 what swollen, with indistinct nuclear membranes, later frequently undergoing 

 chromatolysis. The intestinal cavity contains extruded masses of cytoplasm, 

 intermingled with desquamated epithelial cells containing nuclei in various 

 stages of degeneration. "Der Tod des Tieres wurde durch die voile Degener- 

 ation des Entoderms eingeleitet, wahrend Ectoderm und Genitalanlage noch am 

 Leben bleiben." 



Schultz claimed that the tremendous reduction in the size of Hydra (as in 

 Planarians) during inanition is accomplished chiefly through decrease in the 

 number of cells, the size of those persisting being not very different from the 

 normal. He opposed Roux's theory that those cells persist which require less 

 food in the struggle for existence, stating that in the disappearance of organs 

 during inanition the sequence is in general the opposite to that by which the 

 organism developed, ontogenetically and phylogenetically. This order of loss 

 is not always that most advantageous to the individual organism, however. 



Berninger ('10) obtained results very similar to those of Schultz. He con- 

 sidered Hydra viridis unsuitable for inanition experiments, on account of the 

 symbiotic algae, and studied chiefly Hydra fusca. In ordinary filtered tap water 

 they all died within three weeks, but in spring water they lived twelve to four- 

 teen weeks. As an age difference, Frischholz ('09) noted that newly hatched 

 Hydra fusca die of starvation in four or five days. There is notable elongation 

 in the first week, as observed by Schultz and by Krapfenbauer. The involution 

 changes are not marked until the fifth or sixth week, when the body is reduced to 

 about half its original length (Fig. 7, a to d). In fourteen weeks of starvation 

 the Hydra is reduced from 7-8 mm. length and i}4,-2 mm. width to 0.2 mm. 

 length and 0.13 mm. width. This is estimated to be about }£o of the original 

 size, corresponding to a Hydra embryo a few hours old. Structurally the 

 reduced Hydra differs from the embryo only in the higher differentiation of the 

 cells, and the absence of yolk granules. "Also kann man wohl sagen, dass die 

 Hunger bewirkte Reduktion die Hydra ungefahr auf ein embryonales Stadium 

 zuriickbrachte, wobei der umgekehrte Weg eingeschlagen \vurde, welchen die 

 Entwicklung durchlief." 



Child and Hyman ('19) observed that in Hydra "The differences in diameter, 

 general appearance and opacity between body and stalk become less marked 

 with lack of food and in advanced starvation may almost or entirely disappear." 

 In starved animals, the entoderm becomes much less susceptible to the disinte- 

 grative effect of cyanide, dyes, etc. 



A few observations have been recorded as to the effects of inanition upon 

 other Hydrozoa. Semper ('81) states that "The observations made on Hydroid 

 Polyps by Hincks, Allman and Schneider are highly interesting. According 

 to these, in the first place a Medusa of the group of the Hydroidea can be 



