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spermatogonia derived from primary sex-cells, and vegetative cells 
derived from the peritoneum. During early stages soon after sex- 
differentiation, the spermatogonia are relatively few in number as com- 
pared with the vegetative cells. They undergo constant multiplication, 
however, until at the stage of car. 73 mm, they are quite as numerous 
as the latter (Fig. 11). It is interesting 
to note that none have at this stage 
become transformed into spermatocytes, 
although we found that many oögonia 
had developed into oöcytes in the ovary 
(car. 27 mm). 
testis, but especially during these later 
Fig. 11. Transverse section of a seminiferous 
tubule of a testis from an animal of 73 mm ear. 
length. X 721. 
stages, one finds certain spermatogonia to be smaller than others. 
Their grouping into pairs clearly indicates the fact that their smaller 
size is due to the recentness of cell division. 
In all the history of the testis, it is possible to distinguish clearly 
between spermatogonia and vegetative cells. Neither type undergves 
extensive modification during the early stages. The spermatogonia, 
like the early sex-cells, are distinguishable by their large size, clearly 
defined, spherical cell body, and well rounded nucleus. The vegetative 
cells, like their progenitors of the peritoneum, give only the faintest 
indications here and there of possessing cell boundaries, in general 
they at least appear to form a syncytium. ‘The nuclei are smaller than 
those of the spermatogonia and are either oval or triangular in section. 
In later stages of development, after emergence of the turtle from the 
egg, the nuclei of the actively dividing spermatogonia are frequently 
as small as certain of the vegetative cells. However one has no diffi- 
culty in distinguishing them apart. In corresponding stages of the 
rabbit and pig testis, ALLEN ’04 such clear criteria for differentiating 
them were not in evidence. 
BALBIANI °79, PRENANT ’87, and Bourn ’95 have asserted that 
prior to sexual maturity, there are in the Mammals certain periods 
at which an attempt, as it were, is made to form spermatozoa, but 
that this is abortive, owing to complete degeneration of the spermato- 
gonia, resulting in the presence of but one type of cells, the vegetative. 
The term “prespermatogenesis” has been applied to this phenomenon 
by PRENANT (87). 
Throughout the development of the 
