THE NUTRITION OF THE OVUM OF HYDRA VIRIDIS. 529 



to the quieted body proper. Just as chloretone could not be 

 sent to the closed tentacles, so it appears the endoderm of Hydra 

 cannot send food-material along a narrow channel to its oogonium. 

 The growing oogonium must, therefore, come to the endoderm. 

 As a result of this imposition, by the time the final oogonium has 

 become, through growth, a primary oocyte, an extended relation 

 between the latter and the endoderm has been established. This 

 relation established marks the inception of the second phase of 

 the nutrition of the ovum of Hydra viridis. At the beginning of 

 this second nutritional phase, there are no deutoplasmic in- 

 clusions within the cytoplasm. Soon, however, yolk is formed 

 within the cytoplasm of the oocyte (Fig. 5). This deutoplasm is 

 elaborated by the oocyte out of material taken over in solution 

 from the endoderm and assimilated by the female gamete. Thus 

 the deutoplasm may be looked upon as material elaborated by 

 the oocyte. The deutoplasmic granules are not to be considered 

 the lineal descendants of original nuclei of neighboring interstitial 

 cells that have come to be more and more numerous through 

 amitosis. This position seems logical when we bear in mind the 

 fact that, though many interstitial cells have disintegrated 

 (perhaps most of them) and have been resorbed during the egg's 

 growth, yet, up until maximum surface exposure to the endoderm 

 has been made, no yolk-formation has resulted. Our interpreta- 

 tion is further strengthened by the observation that so long as 

 yolk is making its appearance within the primary oocyte a 

 maximum surface relation to the endoderm is maintained; but 

 when the maximum amount of yolk has been formed the egg 

 retreats from the endoderm as Tannreuther (08) indicates: 

 "After the amoeboid egg becomes filled with yolk, the pseudo- 

 podia are drawn in and the egg becomes nearly spherical" 

 (p. 264), (Text-figure, 3). The second phase of the nutrition of 

 Hydra viridis, therefore, ends with the retreat of the primary 

 oocyte from the mesoglea after it has become filled with deuto- 

 plasm. No deutoplasm is formed thereafter. This phase of 

 nutrition is referred to the development of the zygote. 



SUMMARY. 



The nutrition of Hydra viridis is a dual process, there being 

 two phases. 



