158 OVARIES OF FISHES. 
specimens are not different from those seen in a specimen which is 
certainly immature. 
In May I examined three plaice ; one was a spent female, the right 
ovary measuring 44 inches in length, and 4% inches from the posterior 
end of the ventral fin. There were remains of ripe ova still in the ovi- 
duct, and some partially opaque yolked ova in the germinal tissue. 
The other two were over 15 inches long, and had no yolked ova 
in the ovary, nor any other indication that they had previously 
spawned. 
In June I examined few plaice. On the 9th I opened a female 
143 inches long; the end of the right ovary was 33 inches from the 
anterior end of the ventral fin, 33 inches from the posterior end. 
There were the remains of dead ripe eggs in the cavity of the ovary, 
but at first no trace of yolked ova was found in the germinal tissue ; 
afterwards a few shrunken yolked ova were found, evidently in pro- 
cess of absorption. 
In July, on the 15th, I first found that the formation of the yolk 
in the ova of next season’s crop had commenced. In one specimen, 
16 inches long, the. length of the right ovary was 4% inches, its 
distance from the posterior end of the ventral fin 33 inches. The 
germinal tissue appeared to the naked eye opaque, white, and 
evidently yolked. Under the microscope the majority of the ova 
were seen to contain so much yolk as to be quite opaque, and the 
largest of them were *5 mm. in diameter, that is considerably larger 
than the largest yolkless ova, Fig. 2 shows the appearance of the 
pu. 
Fria. 2.—Ovum of plaice in which formation of yolk has commenced, magnified 
about 200 times. yk., yolk; g.v., germinal vesicle or nucleus with nucleoli at 
periphery. 
smallest ova in which yolk had begun to be formed. Nothing was 
seen to denote that this fish had spawned previously, but considering 
its large size it probably had, 
