DEVELOPMENT OF DISTICHOPORA VIOLAOEA. 141 



Ziegler prove that this is the case. But I shall endeavour to 

 show that we are by no means justified in assuming that 

 amitotic fragmentation is a sign of degeneration. 



In the first place, it can be shown that there is considerable 

 evidence for believing that the oosperm nucleus of some ova 

 does not divide by normal karyokinesis, but does split up 

 araitotically into a large number of minute fragments. 



I have already described (17 and 18) such a process of 

 fragmentation in the case of Millepora, Allopora^ and Disticho- 

 pora, but the following considerations prove that the same is 

 probably true of many other eggs. 



Coelenterata. — In the development of Alcyonium the 

 germinal vesicle entirely disappears, and no traces of the 

 karyokinetic division of the oosperm nucleus can be found. 

 Kowalewsky^ (37) gives a figure of the ovum without any 

 nucleus, but my own observations show that at a stage cor- 

 responding to the one he figures the nucleus is in the form of 

 a number of minute fragments scattered through the substance 

 of the ovum. 



The failure to find karyokinetic division of the oosperm 

 nucleus cannot be attributed to imperfect methods of pre- 

 servation or staining, because young embryos, preserved and 

 stained in precisely the same way as the fertilised ova, exhibit 

 beautiful and typical karyokinetic figures. 



The early stages in the development ofGorgoniacsevolini, 

 described by G. von Koch (36), seem to be precisely similar to 

 those of Alcyonium. In the unfertilised ovum there is a large 

 germinal vesicle containing an excentrically placed germinal 

 spot, but in the eggs that he believed to be fertilised there was 

 no nucleus. ''Ihre Structur weicht von derdes unbefruchteten 

 Eies wesentlich ab. Es fehlt namlich vor allem der Kern, von 

 dem ich keine Spur mehr aufiindeu konnte." The fact that 

 von Koch, after carefully examining over a hundred series of 

 sections through fertilised ova, could find neither traces of 

 segmentation nor the division of the oosperm nucleus, suggests 



' As Kowalewsky's paper is written in the Russian language I am unable 

 to read it. 



