566 Messrs. J. E. S. Moore and G. Arnold. Existence [Dec. 13, 



In Triton the number of the pre-maiotic chromosomes is 24. These in the 

 synapsis unite to form 12 gemini, and consequently we are driven to the 

 conclusion that in the first maiotic spindle figure there exists a pair of gemini 

 belonging to each of the six different types. 



The fact that the varieties are constant in the early spindle figure, really 

 in itself precludes the possibility of the different forms having anything to do 

 with the fortuitous manner in which the gemini may become attached to 

 the spindle fibres, and this indication is enforced to the point of proof by the 

 further observation, which can be readily made, that all six varieties of 

 gemini are present in cells before the nuclear membrane has disappeared,, 

 that is to say, before the spindle fibres have ever acted on them. In fig. 2 we 

 have a drawing of five cells in three of which the nuclear membrane is not 

 yet ruptured, but in each of these three cells representatives of the different 

 classes of gemini are as clearly to be discerned as they are on the early 

 spindle figures. 





a 



b 



c 



d 



e 





9 





h 



Man. 



J? 



H 



2 



6 





4 



z 







) 



z 





Rat 



8 



4 



n 



2 



4 





c] 



2 



(\% 



(6) «x) 

 2 





)! 



(6) Z (a) 



Triton. . sp. 













a 





an 















2 



2 



2 



2 



(ai 2 (b) 



(2) 







Cockroach 







4 



1 



4 









Q 



2 



| 



1 4 









Diagram showing the Forms of Heterolytic Gemini in various Animals. 



Total number Total number 



of gemini. of gemini. 



Man 16 Triton, sp 12 



Eat 16 Cockroach 16 



Another feature which should be noted is the fact that we do not encounter 

 transitional forms passing from one form of the gemini to another ; there is 



