28 INANITION AND MALNUTRITION 



In the medusa Cassiopea, the loss is almost entirely at the expense of the 

 gelatinous ground substance; while in sponges, on the contrary, this substance is 

 increased in amount. The ectodermal structures are more resistant, but they 

 atrophy to a variable extent in different regions. In planarians, the intestinal 

 epithelium, eyes, and pigment tissue and sexual duct system are affected rela- 

 tively early; the muscles atrophy later, while the gonads and nervous system 

 persist with great tenacity. In Lineus, the relative resistance of the various 

 tissues is somewhat similar to that in planarians. Although among the higher 

 invertebrates the skeleton is usually unaffected by starvation, in the snail 

 Helix the calcareous shell is attacked as well as the soft tissues; while in sponges 

 the results appear variable. Calcium deficiency usually causes involution of 

 the invertebrate calcareous skeleton, both in larval and adult stages. In the 

 reproductive passages of Helix, the non-glandular parts appear more resistant 

 than the accessory albuminous gland, which undergoes an enormous involution. 

 While the gland cells are greatly reduced, however, the associated " parenchyma" 

 (stroma) nuclei persist and proliferate by amitosis. 



Effects on the Gonads and Sex. — The effects of inanition upon the repro- 

 ductive system and process have aroused much interest and have been carefully 

 observed in various invertebrates as well as in other organisms. In forms where 

 the process of reproduction may be either asexual by budding, fission or parthe- 

 nogenesis) or sexual, the tendency of abundant nutrition is to favor asexual 

 reproduction; while inanition or other unfavorable environment usually occa- 

 sions a change to the sexual form, in many cases especially favoring the develop- 

 ment of males. The gonads themselves are usually very resistant to starvation, 

 being (like the nervous system) as a rule among the last of the organs to undergo 

 involution. There are, however, evident variations in different species and 

 individuals. 



Among sponges, the process of involution during inanition frequently results 

 in the formation of numerous small bodies ("gemmules"), from which new 

 individuals may be reproduced later. In Hydra, budding is inhibited but the 

 gonads (especially the testes) may mature in spite of the atrophy of the body 

 as a whole. The predominating development of males in Hydra during inani- 

 tion was emphasized by Nussbaum ('93), Schultz ('06) and Berninger ('10), 

 but was denied by Hertwig (06), Whitney ('07), Hanel ('08), Krapfenbauer 

 ('08) and Frischholz ('09). 



In planarians (flatworms), asexual reproduction is inhibited by inanition 

 and there is a return to sexual reproduction, but the "cocoons" are reduced in 

 size and the number of enclosed young markedly diminished. In the nemertin 

 worm Lineus, the gonads undergo partial involution, but some areas (likewise 

 the ducts) are very persistent. 



In the rotifers (wheel-animalcules), Leydig noted that inanition causes 

 prompt atrophy of the ovary and a tendency to production of males. Nuss- 

 baum O97) concluded that in the rotifer Hydatina underfeeding in the phase 

 preceding the ripening of the ovum tends to produce male offspring. This was 

 confirmed by Lennsen ('98) but opposed by Whitney ('08). Shull ('10, '11) 

 concluded that sex in Hydatina is determined by both internal and external 



