26 



BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



Vom Eath, Hacker : — 



My view : — 



a a 

 b b 



a b 

 c d 



As to the question of reduction in the two maturation divisions, only 

 four suppositions can be made: (1) the first division onlv is a reduc- 

 tion ; (2) the second only is a reduction ; (3) both are reductions ; 

 (4) neither is a reduction. As we have now seen, all these suppositions 

 have been made by different authors. We may well say with vom 

 Rath, that "eine allgemein befriedigende Losung ist nur dann moglich 

 wenn die Autoren sich zuerst ilber den Begriff 'Reduction' vollig 

 geeinigt haben." 



The assertion of Hacker and vom Rath ('93), that the resting stage 

 which immediately precedes the first maturation division is sometimes 

 omitted, has intimate connection with the question of reduction, and its 

 meaning, it must be admitted, is not yet entirely explained. The ac- 

 counts of Hacker and vom Rath are too meagre to allow a detailed 

 comparison of the processes in cases where there is no " Keimblas- 

 chenstadium " with those in which it exists. Perhaps we can never 

 settle definitely the question of reduction, but material for its solution 

 should be sought in a careful determination of the origin and meaning of 

 the Vierergruppen. 



Cambridge, May 16, 1894. 



