MATURATION PHENOMENA OF GERM CELLS. 139 



were a longitudinal split, smallest at those periods. In other 

 words, I showed that at the earliest stage when the chromosomes 

 can be distinguished, this space is largest, while the true longi- 

 tudinal split is found in the axis of each arm of a heterotypic 

 chromosome. They add : " L'auteur continue et, sans en donner 

 la moindre preuve cette fois, que les deux brandies de r anse s'en- 

 ronlent r une antoitr dc I'anfi-e pour constituer les dyades enrou- 

 lees, qui, d'apres tous les auteurs, se trouvent dans les spermato- 

 cytes I avant la mise au fuseau des chromosomes." It is only 

 necessary to rejoin that the comparison of the chromosomes as 

 shown in my consecutive figures is sufficient proof. But when 

 they say that my figures " sont fort schematisees," I simply an- 

 swer that is not true, and that all were made with great care with 

 the use of a camera lucida. 



Janssens and Dumez do, however, bring up one good criticism. 

 They note quite correctly that in the spermatogonia the chromo- 

 somes are of unequal lengths, while the two halves of a bivalent 

 heterotypic chromosome are always of equal length. And they 

 reason that if my view were correct that one of the heterotypic 

 chromosomes is formed by the pairing of two univalent chromo- 

 somes, that I would have to demonstrate how two such con- 

 jugating chromosomes are always of the same length. For they 

 argue that if the heterotypic chromosome were formed by a lon- 

 gitudinal splitting, such a splitting would fully explain the length 

 equality of the two arms of the chromosome. 



This is a good criticism, but I find it answered by a study of 

 the relative volumes of the chromosomes in the equatorial plate 

 stage of the spermatogonia. In every case where the pole view 

 shows all the chromosomes lying in one plane, we can determine 

 by carefully drawing them that there are just 12 pairs of chro- 

 mosomes present, the two of each pair being of equal volume and 

 frequently of similar form. One will find many cases where 

 the pole view of a chromosome plate does not show this dis- 

 tinctly, but that is only when the chromosomes are irregularly 

 arranged, and when their long axes do not lie in the plane of 

 the equator. 



A series of figures demonstrate this. Fig. I is the only case 

 where all 24 chromosomes were seen in their entirety on pole 



