Notes on a New Boveri.i species. 9 



division. In this case, the hitherto compact chromatin mass gi^a- 



dually loosens and dissolves itself into separate granules, which 



soon rearrange themselves into short threads irregularly disposed 



in the clear micronuclear space (see m in fig. 7). After that the 



micronucleus takes the shape of a spindle of the usual appearance 



(fig. 8, 7i). The chromosomal threads are now seen to consist 



each of a linear series of minute granules. They are so fine and 



so closely set together tlmt they cannot be counted, nor the mode 



of their distribution exactly be made out. The two spherical 



micronuclei (fig. 9, w. st. and n. w.), resulting from the third division, 



Pig 9 closely resemble in structure the 



, / mother nucleus (fig. 7, ?u) before 



\ \ \\ \\ ' ! / i ' ■' the spindle formation, except in one 



"^^ ' - ! important fact, that the chromatin 



structures contained in either one 

 .^-.- ;^t are noticeably less both in num- 



■A' 



'^•^v 



m=:. 



\ ;%^'^V:- • \-0^J^'*/ ber and in quantity than in the 



?i^t~-'- ■:, . , ] mother nucleus {cf. fig. 7 with 



"' fig. 9). There can scarcely be a 



'"^"'Vj J-"- . doubt that the third micronuclear 



division is a reducing one, brought 

 about by the chromosomal threads in tlie maturation spindle not 

 undergoing a splitting of any kind, and by their becommg dis- 

 tributed in equal parts between the two daughter micronuclei. It 

 is to be mentioned that R. Heutwig (1888) has made out in 

 Paramecium aurclia tliat its sexual nucleus contains about half as 

 many " Chromatin-elemente " as the micronucleus of ordinary 

 individuals. This seems to be very similar to the reducing 

 process in the present case. 



The two micronuclei resulting fi^om the above ripening division 

 in each conjugant are the stationary and the wandering micro- 



