The early development of Eudendrium. 263 



The nucleoplasm becomes more coarsely granular than before, the 

 nucleolus disintegrates, the nuclear membrane disappears and the 

 nuclear contents seem to dissolve and be distributed throughout the 

 cytoplasm. Whether certain of these changes may not be associated 

 with fertilization may well be probable, tho just how far or in what 

 way I have not been able to determine. The whole problem of ferti- 

 lization among hydroids with closed gonads similar to those of 

 Eudendrium is involved in uncertainty. But however this may be 

 there seems hardly any doubt as to the fact of the dissolution of the 

 nucleus about the time of the full growth of the ovum. That it 

 bears some relation to the fact of fertilization is further suggested by 

 the signs of cleavage which follow soon after these changes have oc- 

 curred (cf. Figs. Ô and 6). 



Coincident with this rapid accumulation of deutoplasm by the ova 

 of Eudendrium is the decrease in the size and mass of the entoderm 

 of the surrounding walls of the gonad, a fact which is probably to be 

 interpreted as due to the direct contribution of these tissues to the 

 nutritive metabolism involved. When fully mature the ova of these 

 hydroids is of an orange color and more or less opaque, rendering 

 any critical study of internal changes on the living egg at this time 

 quite difficult or impossible. The abundance of the yolk substance is 

 likewise a barrier of great difficulty to satisfactory fixation and cut- 

 ting of the eggs as well as subsequent staining and clearing. 



Reference to fertilization has already been made incidentally, and 

 little can be added further. So far as I am aware nothing specific 

 is known as to this phenoinenon in such hydroids as Eudendrium, 

 where the ova are enclosed within sporosacs or gonads with thick 

 walls which at no time have direct communication with the outer or 

 inner surfaces of the animal. In the case of Hydra which has been 

 supposed to have its eggs fertilized by sperms penetrating the wall 

 of the ectoderm, this might be possible, where only a thin tissue 

 separated; but with some forms, like the one under consideration, or 

 with Campanularia where a chitinous gonangium must prove a serious 

 impediment to such access, the case is quite different. Examination of 

 the living hydroids repeatedly for some evidence as to the process 

 has as often failed absolutely to afford any satisfactive clue. 



Similar uncertainty as to the phenomena of maturation of the 

 egg prevails. So far as the Eudendridne are concerned nothing is 

 known as to the superficial phenomena, e. g. polar bodies. In many 

 hundreds of eggs sectioned no trace of polar cells could with cer- 



