Helen Dean King 371 
dividuality of the chromosomes would not be maintained any more than 
if a double longitudinal division occurred. Wilcox (59) is, I believe, 
the only investigator who maintains that both of the maturation divis- 
ions are transverse, and his results have not been confirmed by those of 
other workers on insect spermatogenesis. 
If, as seems more probable, synapsis takes place in the spermatocytes 
of Bufo by an end to end union of the chromosomes, the maturation 
divisions are diagramatically represented by Diagram II. The first 
maturation division, through the line XY, separates the univalent chro- 
mosome A from the univalent chromosome B, and is thus a reduction 
division. The second division, through the line Y, separates A into 
two equal parts aa, and B into bb and is, consequently, an equation 
DIAGRAM 1. DIAGRAM 2. 
division. It seems to me a matter of no great importance as to which 
mode of union takes place in synapsis provided that, in the subsequent 
mitoses, one division is reductional and the other longitudinal: the final 
result is the same in both cases. I agree fully with the conclusion reached 
by Grégoire (18), Farmer and Moore (12), and Montgomery (40), after 
an exhaustive résumé of the work done on the maturation phenomena in 
the germ-cells of animals and plants, that reduction occurs in the first 
maturation mitosis, the second division being longitudinal. 
In none of the forms that have so far been studied is the evidence in 
favor of a reduction division in the maturation mitoses of the sperm- 
atocytes more convincing than in Bufo. The mode of formation of the 
dumbbell-shaped chromosomes in the early prophase of the first matura- 
tion mitosis and their later division across the middle of each dumbbell 
furnishes indisputable evidence that the first division is a reduction 
division in the Weismannian sense. That tetrads are normal structures 
in the spermatocytes of Bufo seems also indisputable. I have found 
tetrad groups in large numbers in the testes of adult toads killed at 
