STUDIES OX CHROMOSOMES 
55 
all the stages. The agreement of great numbers of division-fig- 
ures from both testes leaves no doubt regarding the constanc}^ of 
the essential phenomena (with rare minor variations, as indicated 
beyond). As will be seen, the modification of the diploid groups 
has led to corresponding modifications of the maturation-process 
that are most interesting in relation to some of the problems of 
synapsis and of the qualitative differences of the chromosomes. 
DESCRIPTIVE 
a. The spermatogonial groups 
The peculiar anomaly of the chromosome groups, first seen in 
the spermatocyte-divisions, led me to examine the spermatogonial 
groups with particular care, and it will be worth while to state 
both the preliminary and the definitive results. These groups 
are in the nature of the case more difficult than those of the sper- 
matocytes, owing to the greater number, smaller size, and greater 
crowding of the chromosomes; hence, only flat metaphase-plates 
and such as are not very obUque to the plane of section can safely 
be used. A search through the numerous dividing spermatogonia 
showed 35 cases that seemed to meet these conditions and also 
to show no serious obscurity or confusion of the chromosomes. 
Many of these are of almost schematic clearness, and some are 
well adapted for photographic reproduction. The first examina- 
tion showed undoubtedly that 29 of the 35 cases contained 22 
chromosomes each, including 19 large and three very small ones. 
Of the six exceptions, three seemed to lack one of the small ones, 
two, one of the large ones, and one a large and a small. Closer 
study of these six cases ultimately showed that in four cases 
the apparently missing third small chromosome was in reality 
present, though hidden among the larger chromosomes, while in 
two cases an apparently missing larger chromosome was found 
lying immediately below another one, the metaphase-plate not 
yet having become perfectly flat. This leaves but one exception 
in 35 cases, and we shall hardly go astray in the conclusion that 
this exception is probably the result of accident. In any case we 
may confidently conclude that the chromosome-group shown in 
