MATURATION MITOSIS IN AMPHIBIA. 26/ 



that each bivalent chromosome is very probably formed by the 

 union of a paternal with a maternal chromosome, and interpreted 

 this process as part of the phenomenon of conjugation, as a con- 

 jugation of the chromosomes. I showed also that when in the 

 spermatogonia certain chromosomes can be distinguished from 

 the others by peculiarities of size, that such chromosomes pair 

 together in the synapsis ; this was the case in Protcnor, Pcliopelta 

 and Zaitha. McClung (1902) has noted a similar case for An- 

 abrns. A few months ago Sutton confirmed these conclu- 

 sions for Brachystola, and on the basis of a careful examination 

 of the chromosomes has reached the important conclusion, that, 

 maternal chromosomes of a certain length uniting always with 

 paternal chromosomes of the same length, the result of the re- 

 duction division, in separating such two univalent chromosomes 

 from each other, prevents the retention by either of the daughter 

 cells of two chromosomes representing the same characters. 

 Such a result is a strong confirmation of the brilliant postulates 

 of Weismann. 



If it be true that wherever a heterotypic mitosis occurs, it 

 denotes the separation of entire univalent chromosomes, then the 

 old strife of whether a reduction division does or does not take 

 place in the maturation of the germ cells is decided in the 

 affirmative, and we are no longer met by the discrepancy of 

 certain animals with and certain without a reduction division. It 

 rests with the opponents of this view to prove that the hetero- 

 typic division is an equation division, and that has not yet been 

 satisfactorily done. And in reaching this conclusion I may 

 state frankly that at the outset of my studies I was fully con- 

 vinced, almost as much as Herr Meves himself, that the 

 heterotypic mitosis is an equation division ; only long obser- 

 vations have shown me that it can only be regarded as a reduc- 

 tion division. 



McClung has recently (1902) made an embittered attack upon 

 my studies on sperrnatogenesis, due in large part to a misunder- 

 standing of my position. He states at various places that my 

 views are conflicting, and that he is unable to harmonize them. 

 Certain serious mistakes I made in my first paper (1898) I took 

 pains to correct in two others (i 899, 1901), and in these my 

 position is stated very definitely and without contradictions. 



