The first observations were made in January of the present year on
some material prepared by Professor McClung, to whom I wish here
to make most grateful acknowledgment for proposing the line of
investigation, and for many helpful suggestions during the progress
of the same. The testes were those of adult insects, and showed
mostly only mature or almost mature spermatozoa. Enough spermatids
were seen to indicate that their transformation into spermatozoa was
somewhat peculiar.
The material for the drawings was taken from specimens collected
under stones and boards on and near the University campus, at
Lawrence, Kan. Young nymphs of _Gryllus_ were caught as early as
March 1, but the cells of the testes were all in the spermatogonia
and spermatocyte stages. During the early part of May, after the
nymphs had passed their third molt, crickets were secured whose
testes showed all stages of development and transformation.
_Gryllus assimilis_, the common black field cricket, has paired
testes lying in the anterior dorsal part of the abdomen. These have
a whitish transparent appearance, which becomes duller in the adult,
showing sometimes a slight yellowish tinge. The shape of each is
that of a somewhat conically rounded body, not unlike a flattened
strawberry. Each testis consists of a central rachis about 3 mm.
long, from which extend a large number of curved follicles varying in
length from 1 to 3 mm.
The follicles are larger toward the blind end and taper toward
the rachis. Each follicle is divided into cysts, but more often
transversely than longitudinally, for frequently one cyst occupies
the whole follicle in cross-section. The cysts toward the rachis end
of the follicle are much longer and narrower than those of the blind
end. The cells are not very large and contain twenty-four chromosomes
in the spermatogonial generations; eleven and twelve were most
frequently found after the reduction.
The follicles of the cricket testis show the different cell
generations and the same relative arrangement of them as McClung
(’00) found in _Hippiscus_, and Sutton (’00) in _Brachystola_.
The spermatogonia are nearest the blind end of the follicles,
spermatocytes next, and the spermatids following the latter. The
cells of a cyst are not, as in _Anasa_ (Paulmier, ’99), “in the same
stage of development,” but only approximately so, for some cysts show
cells in the metaphase, while others have reached the telophase.
Successive cysts, as in _Brachystola_, do not show successive stages;
for, frequently, growing spermatocytes and late spermatids, or even
young spermatozoa, were observed side by side. The individual cells
in division pass through prophases, metaphases, anaphases, and
telophases—these terms being used according to their usually accepted
meanings. (See McClung, ’00.) In this paper I shall begin with the
cell when it has reached the telophase of the second spermatocyte
division; that is, just after the chromosomes have reached the poles
of the spindle.