Notes ou some Hydromedusae frorn the Bay of Naples. 565 



The differences as to the exact means bv which the g-rowiug 

 eggs appropriate the surrounding germ cells which characterize the 

 accounts of CiamIcian, Brauer, and Doflein, seem to me to he 

 similar to others already cited as to the regiou where they originate, 

 etc., namely, a dift'erence of Interpretation and deiinition, rather thau 

 of fact. As I have shown in the case of Pennaria tiarella and ca- 

 voUni^, so it seems Avith species of Tubidaria, there may he differences 

 as to points of detail. In some cases the eg-g may engulf the germ 

 cells hodily, later reducing them to a fluid coudition ; while in others 

 this reduction appears to take place before absorption. But whether 

 before or after, it must ultimately depend upon some process of 

 reduction substantially digestive in character before final assimi- 

 lation is accomplished. The only other alternative to the suppositiou 

 is that of mere fusion of the protoplasm of the one with that of 

 the other without any assimilative changes whatsoever. That this 

 is not the case would seem to be proved by the fact of the per- 

 sistence of these so-called pseudocells or nuclei within the eggs 

 during the entire history of growth, and even that of development, 

 as is well known by those wlio have concerned themselves with the 

 subject. Apparently the disintegration, or reduction of these nuclei 

 takes place much less rapidly than does that of the cytoplasm of 

 the germ cells, so that they may be distinguished within vacuoles 

 of the growing, or developing eggs long after their first incorpo- 

 ration. 



Maturation and Pertilization . 



Concerning these phenomena there is little to add to the earlier 

 researches of Ciamician and Brauer. It has not been possible to 

 confirm the Observation of the former that during the process of 

 maturation the eggs become more or less conica! ou the side from 

 which the polar bodies are extruded. Since, however, his obser- 

 "vations were made, in part at least, upon living eggs, while, upon 

 this phase of the subject, my own observatious have ali been upon 

 preserved material, there may be no definite contradiction. It would 

 seem to me doubtful, however, whether any appreciable change of 

 form could be observed upon eggs enclosed in fixed gonophores within 

 which they are usually closely packed. 



Brauer's account is much fuUer and more definite than is that 



' Arch. Entwicklungsmech. IS. Bd. 1.904 pag. 457. 



