DEVELOPMENT OF THE EGG OF CLAVA LEPTOSTYLA. 229 



to say, though it seems altogether probable. At any rate, the 

 facts seem clearly to justify the general conclusion that for a time 

 in the early history of the development of this egg nuclear ac- 

 tivity differs very greatly from the ordinary forms of mitosis, and 

 appears to involve direct, or amitotic division. During later 

 cleavage abundant mitosis clearly indicates the prevalence of this 

 form of cell division, if, indeed, it may not wholly supersede the 

 other, though its appearance during regenerative activities shows 

 the possibility of its recurrence under various conditions. 



I have called attention to similar nuclear phenomena in the de- 

 velopment of Endcndriiun and Pcnnaria, and in the earlier paper 

 ('O4 2 , p. 267), cited observations of similar sort from several 

 sources. More recently still other cases have come to light, and 

 it seems altogether probable that as facts multiply and attention 

 is focused upon the phenomena cytologists will be forced to take 

 cognizance of this form of cytogeny and give to it something 

 more than a merely incidental place in cellular activities, and 

 assign to it something more than senescent significance. 



Among the more recent data bearing upon this point may be 

 cited, first, the observations of Osborn ('04), in connection with 

 the development of Fasciolaria ; and second, similar observations 

 by Glaser ('05), on the same organism, which go to substanti- 

 ally confirm the facts noted by Osborn, though with somewhat 

 different phases of interpretation. Still a third series of facts are 

 brought to light by Child ('04) in a paper on " Amitosis in 

 Moniezia," in which he clearly shows the prevalence of this form 

 of cell division in the growth of the reproductive organs and the 

 development of the sexual cells, and expresses the belief that 

 " future investigation will probably show that amitosis is at least 

 as important in the life of the cell as mitosis." 



As I have elsewhere pointed out, it is well known that cell 

 division in Protozoa exhibits very different cytological features 

 than do cleavage cells in early ontogeny. 



In many, mitosis seems to be entirely lacking, while in most 

 its features are difficult to correlate with the more typical features 

 in metazoa. Just why we should insist upon finding among a 

 class like ccelenterates all the details of cytogenic mechanics 

 more or less familiar in vertebrates or other higher groups of 



