34 



INANITION AND MALNUTRITION 



cells markedly loosened and dissociated; inner mass of cells usually compact, 

 may show rudimentary gastrula cavity. "Die Zwischensubstanz ist auffallend 

 schwach entwickelt." 



When adult sponges {Sycandra) are placed in the CaC03-free solution, the 

 skeleton shows little or no obvious change, although the soft parts are affected. 

 The histological changes are somewhat similar to those seen in the experi- 

 ments with larvae. "Im Innern des Tubar-Hohlraums zeigt sich Detritus mit 

 Porenzellen; die Gastralzellen geben ihre histologische Auspragung auf, ballen 

 sich zusammen.'" In the gastral cells, karyokinesis may continue long in the 

 CaCCVfree solution. In completely Ca-free solution, the skeleton of the adult 

 sponge Sycandra is but slightly affected. The soft parts, however, degenerate 

 in a manner resembling the normal process of gemmulation. 



Maas later ('07, '10) studied the effects of ordinary inanition upon sponges 

 (and other organisms with calcareous skeleton). In Ascandra Lieberkiihnii 

 and Sycon raphanus, while in Ca-free medium the skeletal spicules disappear 

 and the soft parts persist, during ordinary inanition (deprivation of food) 

 the converse occurs. During hunger involution the organism is reduced in 

 size, with involution of the old osculum, degeneration of part of the sponge and 

 formation of a new osculum (sometimes two). The body becomes irregularly 

 lobulated externally, with syncytial structure and excessive gelatinous ground 

 substance internally. A similar reduction of the calcareous skeleton with per- 

 sistence of the soft parts was observed in certain molluscs, the tube-worm 

 Spirorbis, and Foraminifera (Bilociilaria and Quinquelociilaria) . 



The involution changes produced in sponges by unfavorable conditions 

 (Ca-deficit, general inanition, etc.), according to Maas ('10), all involve loss of 

 cellular differentiation (dedifferentiation). Through phagocytosis, syncytia 

 arise which are considered equivalent to "gemmules." The body is reduced 

 to a 2-layered condition, but these layers are not comparable to the normal germ 

 layers. Wilson ('07), Urban ('10), and Miiller ('n), likewise obtained experi- 

 mentally a reduction or degeneration of sponges, with the ultimate formation 

 of gemmule-like bodies. It is not clear, however, to what extent inanition was 

 a factor in these cases. 



COELENTERATA 



Among the Coelenterata, observations upon the effects of inanition, aside 

 from a few studies on Scyphozoa, and a single observation on Ctenophora, have 

 apparently been confined to the class Hydrozoa. Of the Hydrozoa by far the 

 greater number of investigations have concerned the fresh-water polyp, Hydra, 

 which will be considered first. 



Hydrozoa. — The earliest recorded inanition experiments on Hydra were 

 those of Trembley (1744), who noted that both Hydra viridis and Hydra fusca 

 required four months for death from starvation. Retrogression and premature 

 detachments of buds during inanition were also observed. "Quand la nourri- 

 ture manque, les jeunes polypes se separent plutot. II est apparent que, presses 

 par la faim, ils se detachent pour aller chercher ailleurs de quoi la satisfaire" 

 (I.e., p. 159). This was confirmed by Marshall ('82) and Berninger ('10). 



