528 WM. A. KEENER AND J. B. LOOPER. 



are passing" (p. 263-264). The contrast between what Tann- 

 reuther herein describes and our observations appears in two 

 ways. In the first place, if yolk formation depends upon the 

 disappearance of the interstitial cells of the ovary, then yolk 

 should appear when these cells disappear. They are clearly seen 

 to disappear throughout the growth of the oogonium and yet 

 until the latter has reached its full growth no yolk has appeared. 

 In the second place, we find that no interstitial cells have been 

 bodily taken up or ingested as shown by Tannreuther in his Fig. 6. 

 His Fig. 6, however, is not, in itself, convincing; for he shows the 

 so-called nuclei leaving only two interstitial cells. Moreover, the 

 cells from which these nuclei are migrating show no marked 

 cytoplasmic change. Likewise, his written observations are not 

 convincing with reference to the manner in which yolk arises. 

 He makes the significant statement that "The pseudopodia do 

 not grow out between the cells of the ovary, but rather between 

 the ovary as a whole and the mesoglea" (p. 263). If, now, the 

 pseudopodia were sent out with reference to yolk formation, 

 dependent upon the interstitial cells of the ovary, they would 

 "grow out between the cells of the ovary" and not "between 

 the ovary as a whole and the mesoglea." 



There is no meaning in the extensive application of the primary 

 oocyte's pseudopodia to the mesoglea, if the yolk granules are 

 derived from the interstitial cells. On the other hand, we see 

 in this spreading out of the primary oocyte over the mesoglea a 

 method of making maximum contact with a source of food 

 material upon which to draw for the elaboration of deutoplasm. 



In Hydra, the endoderm is the source of food supply. Kepner 

 and Hopkins (24) observed that, as a diploblastic animal, Hydra 

 cannot transport widely material absorbed by the endoderm. 

 For example, chloretone injected into the enteric cavity of Hydra 

 effects only the adjacent ectoderm of the body proper. The 

 sphincters at the bases of the tentacles prevented the injected 

 chloretone entering the latter and the compression of the walls 

 of the peristome prevented chloretone entering its lumen . It was 

 thus of interest to observe that the tentacles and peristome 

 received none of the chloretone that had been absorbed by the 

 general endoderm, for they became unusually active in contrast 



