195 
On spawning a very marked change takes place. 
Fig. 21 represents the condition of a mature and spent 
female. The ovary is seen to be considerably retracted, 
and is only just visible on opening the body cavity. Its 
walls are soft and flaccid, and enclose a large cavity. The 
posterior extension still exists, and is indeed not much 
shorter than in the ripe specimen. The condition of the 
fish is indicated externally by a shallow groove running 
backwards on either side in the position formerly occupied 
by the pad spoken of above. The flesh is lean, and the 
fish is generally regarded as in poor condition as a food. 
It appears* that after spawning the ovary never 
reverts to its former immature condition. That is, it 1s 
always possible to distinguish between a spent mature, 
and an immature fish. Similar contrasts are exhibited 
by the various phases of the testes, but on account of the 
relatively small volume of these organs the changes are 
not so striking and afford no external indications. 
The ovary of the Plaice, like that of the majority of 
Teleostean fishes is a sac the wall of which is continuous 
with that of the oviduct. This is the cystoarian condition, 
and for an understanding of the morphology of such an 
ovary the other common type met with among Teleostei, 
the elasmoarian ovary, must be studied.t The internal 
wall of the cystoarian ovary corresponds to the external 
face of the peritoneal lamella which forms the elasmoarian 
organ, and to the outer visible surface of the ovary of an 
Klasmobranch fish—the surface from which the ova 
dehisce into the general body cavity. There can be no 
doubt from the work of Balfour and Parker on Lepi- 
dosteus, that the cavity of the cystoarian ovary into which 
* See Holt, Journ. Mar. Biol. Ass., vol. ii., p. 363. 
+ See Howes—Hermaphrodite genitalia of the codfish. Jour. Linn. 
Soc., London, vol. xxiii., 1891, pp. 539-557. 
{ Structure and development of Lepidosteus, Phil. Trans,, vol. clxxiii., 
Part 2, 1882. 
