No. 6.] DEVELOPMENT OF PARYPHA CROCEA. 299 



inner side so that it resembled the figure shown by Hickson ('90) 

 to illustrate the stage in the fragmentation of the oosperm 

 nucleus of Allopora. In the next stage the nuclear membrane 

 is broken down and the nucleoplasm blends with the cytoplasm 

 of the egg, from which it can only be distinguished by its 

 homogeneousness and greater transparence (PI. II, Figs. 7, 8). 

 In other eggs having the same general appearance as the last 

 no nucleus whatever is visible. I have several complete series 

 through eggs in this stage, none of which show any signs of a 

 nucleus, although they have been stained by a number of dif- 

 ferent processes, and I am perfectly confident that the nucleus 

 would be visible if present. Hickson describes a similar con- 

 dition in the eggs of Allopora, Milleopora, and Distichopora ; 

 and Dr. C. W. Hargitt tells me that in his opinion a like condi- 

 tion is to be found in Eudendrium, although he has not yet 

 placed it beyond doubt. 



Hickson ('93) has written an extended account of " nuclear 

 fragmentation," in which he cites the opinion of a number of 

 authors with regard to this much disputed question. After 

 describing the stages observed in Distichopora he says : " I 

 have described a process which can only be compared with the 

 so-called free nuclear formation in the early insect embryos. 

 Nuclei make their appearance in places which were previously 

 devoid of any nucleus or nuclear structure. It is not reason- 

 able, however, to assume on the insufficient evidence before us 

 that " nuclear formation " does actually occur. It seems to me 

 much more probable that minute fragments of nuclear sub- 

 stance scattered through the protoplasmic meshwork collect 

 together in places, and form by their fusion true recognizable 

 nuclei. In other words, the process we have under observa- 

 tion is rather one of "nuclear regeneration " than one of free 

 "nuclear formation." He quotes Flemming and Ziegler as 

 authorities most opposed to this view, both these investigators 

 contending that any process of nuclear division other than that 

 by mitosis is a sign of the degeneration of the nucleus and the 

 approaching end of the life of the cell. Ziegler inclines to the 

 opinion that nuclei which have arisen by amitotic division will 

 never again divide mitotically. Opposed to these are the works 



