MITOT1C DIVISION OF BINUCLEATE CELLS. 97 



the binucleate follicle cell there are 12 large, 8 small and ^2 

 intermediate ones. Similar double chromosome plates have 

 been found in the follicle cells of other insects, e.g., Anasa (\Yil- 

 son, '06) and are probably likewise due to the division of a 

 binucleate cell. 



In the anaphase (Fig. 9), the two sets of chromosomes cannot 

 be distinguished, and the two spindles appear always to be fused. 

 It is difficult to tell exactly what happens in the telophase. It 

 would seem that a membrane formed around the group of chro- 

 mosomes at each pole, (Fig. 10), each daughter nucleus becoming 

 elongated and that it later separated off into two nuclei (Figs. 

 ii and 12). It seems entirely possible that in such a separation 

 into two nuclei, which would resemble a nuclear amitosis, the 

 chromosome content might be so distributed that each nucleus 

 would maintain the chromosome constitution characteristic of 

 the species. It is possible that the separation into two nuclei 

 occurs only in those cases where the original sister nuclei did 

 not become entirely fused and that when they are fused, each 

 daughter nucleus remains as an abnormally large nucleus, 

 really double in nature. It is evident, however, from the series 

 of figures that two binucleate cells may arise by the mitotic 

 division of a binucleate cell. 



Although the binucleate cells of the follicular epithelium have 

 been believed by some observers (Preusse, '95, De Bruyne, 

 '97, Gross, '01), to arise by an amitotic division, I have found 

 no evidence of such an origin, and would believe it probable 

 that they arise by the failure of cell division after a nuclear divi- 

 sion by mitosis. Macklin ('16) has described a process of amito- 

 tic nuclear division in his study of binucleate cells in living tissue, 

 but the figures he gives might also be interpreted as the last 

 stages in the mitotic division of a binucleate cell as described 

 above. If binucleate cells do arise as Macklin believes and his 

 interpretation of them as potentially mononuclear, is correct, 

 there must be two types of binucleate cells. In one type, each 

 of the two nuclei has a complete set of chromosomes, as described 

 above. In the other type, the two nuclei taken together have a 

 complete set of chromosomes. Macklin was, however, unfor- 

 tunately unable to verify his assumption as to the chromosome 



