EFFECTS ON THE HIGHER INVERTEBRATES 35 



Baudelot ('69), Kleinenberg ('72), Marshall ('82), and Schultz (06) found 

 that in underfed Hydra, well-formed buds, instead of becoming detached, may 

 undergo reduction, retrogression and final disappearance. 



Greenwood ('88) described the changes in the entoderm cells of Hydra during 

 the earlier stages of inanition. The nutritive vacuoles (containing protein and 

 fat) persist for two or three days, but become fewer and smaller or disappear 

 entirely in more protracted fasting. The smaller "gland cells" of the entoderm 

 become progressively more conspicuous, but in prolonged starvation their 

 secretory granules may become smaller and partly dissolved. The pigment, 

 though abundant during inanition, may also be slowly discharged. 



Tentacles 



-Testis 



9. 



n s r 



Fig. 7, a to d. — To illustrate the changes in size and external form of the fresh-water polyp. 

 Hydra fusca, during starvation. All Xio. (After Schultz '06.) a, Normal Hydra; b, Hydra 

 starved 1J-2 weeks; size reduced, but form still nearly normal; c, later stage of reduction; 

 tentacles have become rudimentary; the testis has matured, in spite of the atrophy of the body 

 as a whole; d, terminal stage of reduction (cf. Figs. 8-1 1). 



Nussbaum ('87, '93) was the first to study the effect of inanition upon sexual 

 development in Hydra. He concluded that the (normally hermaphroditic) 

 Hydra when abundantly fed will produce ovaries only; when moderately fed, 

 both ovaries and testes; while those scantily fed produce testes only. This 

 question is of fundamental importance in the theory of sex-determination, and 

 has occasioned much controversy. 



Hertwig ('06) opposed Nussbaum's view, and maintained that the condi- 

 tions for sexual differentiation in Hydra are more complicated, temperature 

 being a more important factor than nutrition. In his colony, sex-organs 

 (always male) appeared only at lower temperature, whether starved or well-fed. 

 The testes were better developed in the well-fed. 



