WILCOX: SPERMATOGENESIS. 25 



Diagram II. serves to represent the view of Hacker, Weismann, vom 

 Eath, and others. Tlie iii'st division is here seen to be an equation di- 

 vision. But none of these authors has offered any reliable criterion by 

 which we may judge whether it is the " sister idants " or tlie " non-identi- 

 cal idants " that are separated by the first division. They have presented 

 no satisfactory evidence that in the same nucleus all groups undergo either 

 a reduction division or an equation division. How are we certain that 

 one group does not undergo a reduction division at the same time that 

 another in the same nucleus passes through an equation division ] This 

 possibility, as shown in Diagram III., is not excluded. Hacker ('92, 

 Fig. 22, and '93, Fig. 116) believes he has seen two examples where the 

 non-identical idants were still in connection with each other after sepa- 

 ration of the sister pairs in the formation of the first polar globule, but 

 the figures are rather unsatisfactory. 



This discussion will, I hope, have made one thing clear : the abso- 

 lute necessity of a knowledge of the origin of the Vierergruppen, in 

 order to a proper interpretation of the reduction question. If Brauer's 

 account of the origin of the Vierergruppen be correct, there can be 

 no reduction. If Hacker and vom Rath have rightly described their 

 origins, there is one, and only one, reduction. If my description of the 

 ring formation be accurate, there may be two reductions. I am quite 

 willing to grant that, as Brauer maintains, precocious preparations for 

 both divisions are made in the prophases of the first spermatocyte di- 

 vision. But Brauer maintains an origin for the groups of four, which 

 determines that each group shall consist of four identical elements, and 

 thus does away with Weismannian reduction, while I contend that, 

 owing to the manner of their origin, all four elements may be differ- 

 ent or unlike one another, and therefore that both divisions may be 

 reductions. 



The fate of a Vierergruppe, according to the four views mentioned, 

 may again be brought together in diagrammatic form for comparison. 



Brauer : — 



Henking : 



a a a a 



a a a a 



a 



a 



a . a 



a a a __ 



h h h * * h b 



