26 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Vom Rath, Häcker : — 
a aa ala ala 
b b b bb blb 
My view : —. 
alb 
ab ojd alb 
cd rpm 
y c|d 
cd 
As to the question of reduction in the two maturation divisions, only 
four suppositions can be made: (1) the first division only 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 Lósung ist nur dann möglich 
wenn die Autoren sich zuerst über den Begriff ‘Reduction’ vóllig 
geeinigt haben." 
The assertion of Häcker and vom Rath (93), that ¿he 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 Häcker and vom Rath are too meagre to allow a detailed 
comparison of the processes in cases where there is no “ Keimbläs- 
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, 
