No. 2) THE OOGENESIS OF BUFO LENTIGINOSUS. 417 
first maturation mitosis occurs is the transverse axis of the 
_ chromosome at an earlier period (King, 51). In both matu- 
ration mitoses the bivalent chromosomes are divided longitu- 
dinally (Text-Figure I, A). 
If synapsis occurs when the germinal vesicle disintegrates 
then the chromosomes must have united end to end, as shown 
in Text-Figure I, B, otherwise both of the maturation mitoses 
are equation divisions of bivalent chromatin segments and in 
neither division are univalent chromosomes separated (Text- 
Figure I, C). The investigations of Stevens (87, 88) have 
shown that in Sagitta synapsis takes place in the egg by a 
side by side conjugation of the chromosomes and in the sperm- 
- atocytes by an end to end union. This is probably the plan 
that is followed in the germ-cells of Bufo if synapsis occurs 
in the egg during the synizesis period. I am inclined to the 
opinion that in the egg of Bufo, as in the spermatocyte, synap- 
sis occurs shortly before the maturation mitoses and that the 
chromosomes are united end to end. On this assumption the 
first maturation division in the egg is a reduction division in 
the Weismannian sense since it separates univalent chromo- 
somes, and the second division only is an equation division 
(Text-Figure I, B). 
A. and K. E. Schreiner (80-82), who have recently exam- 
ined the chromatin relations in the germ-cells of many differ- 
ent forms, conclude from their studies that in the germ-cells_ 
of all animals the chromosomes conjugate in pairs during 
synapsis, never end to end. This generalization finds an ex- 
ception in the germ-cells of Bufo. In the spermatocytes of 
this amphibian synapsis occurs during the synizesis stage whicn 
immediately precedes the prophase of the first maturation mi- 
tosis, and in the prophase and metaphase of division the chrom- 
osomes behave in such a way that there seems no possibility of 
avoiding the conclusion that they were united end to end in 
synapsis. In the egg, as I have shown, it is not possible to 
determine when or how synapsis occurs; yet the evidence at 
my command seems to indicate that in synapsis the chromo- 
somes are united end to end as they are in the spermatocytes. 
