THE STURGEONS AND STURGEON INDUSTRIES. 
251 
of the further differeutiation of the protova and the manner in which the small laminse 
with the involuted germinal epithelium between them becomes indifferently converted 
into ovarian lobules or seminiferous tubules remains to be worked out. 
All of the data bearing on the development of the internal reproductive organs 
given above have reference to the common sturgeon, A. sturio, but I fortunately 
hai^pen to be in possession of materials from young individuals of the smaller species 
A. brevirostris, which will probably throw light upon this asj)ect of the subject. 
All of the young specimens of A. brevirostris which I have been able to obtain 
show the internal reproductive organs in a more advanced condition of development 
than young individuals of A. sturio of the same size. In A. brevirostris measuring 
from 18 inches to 2 feet in length the sexes could be very readily distinguished, since 
the internal reproductive organs were either testes or ovaries according to the sex. 
In the ovaries the young ova were distinguishable as such in the ovarian tissues, with 
a pocket lens, and in the males the testes had assumed the opaque pinkish- white tint 
of those organs in the adult male. In the young female of A. brevirostris, however, 
the young ova had not yet shown any tendency to develop pigment granules within 
their superficial protoplasm ; in other words, they were found to be of the same very 
pale amber color as the completely spent rocs of the adult female of A. sturio. The 
young male of A. brevirostris showed the seminiferous tubes of the testes developed, 
but there were as yet no signs of the production of spermatozoa in sections of the 
organ. 
In both sexes of the young of A. brevirostris the reproductive organs, both ovary 
and testis, are found embedded in depressions on the inner face of a rich, creamy- 
yellow body which is considerably more voluminous than the reproductive tissue itself. 
This yellow body is composed in great part of fatty tissue, and there is but little 
doubt that it is developed from the uou-reproductive portion of the genital fold lying 
on either side of the tract of transverse laminae already described as being found in 
a much earlier stage of the reproductive organ in A. sturio. 
The later history of this fatty body shows that it does not keep pace with the 
growth of the proper reproductive tract, which becomes more and more voluminous as 
sexual maturity is reached until the ovary becomes the bulkiest organ in the body- 
cavity, as shown in the ventral view of the adult female with the nearly mature roes 
exposed, as shown in Plate LI. In the mature male there is relatively more of the 
fatty body present than in the female, in which it is completely concealed from view 
by the great size and width of the lobules of the ovary. What remains of the fatty 
body underlies, and is closely adherent to, the basal membranes by which the ovaries 
and testes are suspended to the dorsal walls of the abdominal cavity. These mem- 
branes form a mesovarium and mesorchium in the female and male respectively. 
These structures are, in both cases, derived from the basal part of the genital folds, 
which remain narrow at the base in cross-section, while the reproductive tract widens 
and becomes very voluminous at its distal end and depends into the abdominal cavity. 
The changes which take place in the course of the development of the roes to 
maturity, as a result of the increase in the size of the vast number of ova of which 
they are largely composed, is of great interest. While the young ova are still em- 
bedded in the narrow ovarian lamellae they show a tendency to aggregate the yolk 
material at one side, while the globular nucleus, with numerous chromatin spherules 
adherent to its walls in a single layer, is more or less peripheral in position. As soon 
