270 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
eggs, the pigment being diffused in fine particles throughout the substance of the egg 
of the sturgeon, somewhat as it is throughout the ovum of the batrachia. The next 
grade of coloration of the roe is a very much darker one ; brownish, with a decided 
shade of gray or lead color, when the roe is viewed as a whole. This last-mentioned 
shade of roe, which is quite common, is known as ‘‘light roe” amongst the packers 
of caviare. Several gradually darker shades may be recognized between this last- 
named variety and the next, or the quite “ dark roe ” as it is called by the dealers, who 
are careful not to mix the lighter and darker kinds together in the manufacture of 
caviare; the reason for which is, that the light aud dark eggs when mixed together 
give to the caviare so prepared a “ pepper aud salt ” appearance which is not considered 
desirable by dealers. 
These differences in the color of the roes is wholly due to the presence of more or 
less pigment in the individual eggs. The germinal area or disk of the eggs of the 
dark roe is almost black, while in the light roe this area is not so dark, and there is 
a distinct dark dot or spot in the center which is surrounded by a light zone, outside 
of which there is a much darker superficial ring of pigment which marks the edge of 
the germinal area. 
The internal reproductive organs or testes of the male sturgeon are not nearly so 
large as the roes of the females, which may vary in weight from about 50 to as much 
as 120 pounds. The testes probably never much exceed 10 or 15 pounds in weight, 
and are cream-colored, with a shade of pink, instead of having the dark tint which 
characterizes the roes of the females. The form of the testes is that of a compressed 
irregular series of bodies, separated from each other by narrow constrictions, aud 
present as paired organs on either side of the mesentery. In cross-section the seg- 
ments of the testes are oval, the mature, sexually active organs being nearly 2 inches 
thick and 3 to 4 inches wide, and extending for a distance of 18 inches to 2 feet on 
either side of the body-cavity. The transverse subdivisions of the testes is subject to 
variations in different individuals, some having them subdivided into a greater num- 
ber than others. 
When the testes are mature, upon cutting them across, the larger ducts will be 
made apparent from the readiness with which the milk-white, viscid seminal secretion 
escapes from their cut ends. The testes may be removed from the living male and the 
semen, or milt, pressed from the fragments, especially from the larger ducts found 
along the dorsal border of the organ. I have upon two occasions tried to fertilize the 
eggs with milt pressed from fragments of the testes, but without success; yet this 
experience is not to be taken as conclusive that it may not be done. In both cases 
the ova which were at my disposal were probably not in condition to be fertilized. 
Where large numbers of the eggs of the sturgeon are to be fertilized, I think that it 
may be necessary to resort to this method, as I find that it is somewhat difficult to 
press out much milt from the testes by means of pressure upon the abdomen of the 
sexually mature male. If the abdomen is firmly pressed with the foot, accompanied 
by a firm backward stroke of the leg, a few drops of a milky secretion are forced out 
of the geuito-uriuary opening just behind the vent. The secretion forced out in the 
manner described is thin and watery, not being much more consistent than skimmed 
milk, whereas the secretion from the ducts of the testes is intensely white, glairy, and 
viscid, but readily breaks up aud thins out in the presence of water to form a milky 
mixture, swarming with spermatozoa. The ‘Only successful results in fertilizing the 
