MATURATION PHENOMENA OF GERM CELLS. 149 



continuous /////;/ spirem, which probably does not break into 

 segments until the metakinesis of the first maturation mitosis, but 

 no continuous chromatin spirem. Hence it is not a question of 

 chromosomes which were already contiguous remaining con- 

 tiguous, but of chromosomes which were first separated (except 

 for their linin connections) conjugating to form pairs during the 

 synapsis stage. The criterion of the synapsis stage is such a 

 pairing; and the term "conjugation" of the chromosomes rep- 

 resents the facts much better than the term " reduction in 

 number." 



The bivalent chromosomes so formed by conjugation, in the 

 Hemiptera, Peripalns and Amphibia, become so placed in the 

 equator of the spindle of the first maturation mitosis, that entire 

 univalent chromosomes become separated. This is a true reduc- 

 tion division in the sense of Weismann. Each spermatocyte 

 of the second order thus receives whole univalent chromosomes 

 in one half the normal (somatic) number. While the majority 

 of writers still hold that no such reduction division occurs, the 

 idea being abhorrent to them, there are still a number who have 

 furnished an array of facts that can be interpreted only as speak- 

 ing for such an occurrence ; thus Riickert, Hacker, Vom Rath, 

 Korschelt, Henking, Paulmier, McClung, Sutton, Nichols, Grif- 

 fin, Van Winiwarter, Lillie, Schockaert. But the arraying of 

 names on the one side against those on the other is no argument 

 in itself, and we may pass to the discussion of certain facts which 

 harmonize completely with the occurrence of a reduction division, 

 and remain unexplainable on any other basis. 



First, it may be recalled that there is a divergence of opinion 

 as to which of the two maturation mitoses is the reduction divi- 

 sion, some holding that it is the first and others, the second. 

 There is no good reason, save the probability that there would 

 be expected uniformity in such important processes, that this 

 division should always be in the first mitosis, or always in the 

 second ; for it. is quite possible that there is a difference in this 

 regard in different objects. In the discussion which follows we 

 will assume it to be the first maturation mitosis since there 

 occurs the reduction division in the objects specially studied 

 by me. 



