158 A. RICHARDS. 



mitosis is of the most positive character. It cannot be too 

 strongly emphasized. 



Eighth, I have after diligent search upon carefully prepared 

 material been unable to establish a series of stages in the auto- 

 constriction and subsequent division of the nucleus and cell body 

 by amitosis. 



Considering the evidence as set forth, it seems to the writer 

 that one is forced to the conclusion that mitosis is the method 

 by which pre-oogonial, oogonial and cleavage divisions are accom- 

 plished. These are the divisions to which the chief interest 



attaches. 



DISCUSSION. 



Since the account of Child appeared describing amitosis in 

 Moniezia and other forms there have been a number of a priori 

 suggestions offered by various workers as possible explanations 

 of the conditions which he describes. It will be of interest to 

 examine some of these suggestions in the light of the facts which 

 I have observed in Moniezia. 



Gary on the basis of his observations on Diplodiscus suggests 

 that the telophase of an intranuclear mitosis would give all the 

 appearances of true amitoses. I have carefully searched for 

 evidences of intranuclear mitoses in Moniezia but have found 

 none. I have seen cases which at first resembled a faint intra- 

 nuclear spindle, but upon more careful study it became clear 

 that they were merely chance arrangements of linin threads and 

 chromatin granules and not mitosis. Furthermore, as already 

 shown, distinct cases of mitosis of the regular type are not difficult 

 to find. It is, of course, true that the condition which Cary 

 describes would resemble amitosis, but I have not found it 

 present in Moniezia. 



Boveri calls attention to the fact that figures similar to those 

 found in Amblystoma (Child, o~a) are also found in Triton. In 

 this latter form Rubaschin found that after mitosis the nuclear 

 material does not fuse to form a single vesicle in the blastomeres 

 but two are always formed. They never separate but go through 

 mitosis together. In Moniezia there is no evidence of this kind 

 of phenomenon. 



As there is no " Nebendotter " in the eggs of Moniezia my 



