338 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



posterior wall of the body cavity. At this age, and for 

 some considerable time afterwards, it is quite impossible 

 to distinguish between male and female gonads without a 

 microscopical examination. The growth of ovaries or 

 testes is extremely slow during the first two years of life, 

 that is up to 6-8 inches long. After this age the ovary 

 can be readily distinguished from the testis. It is a 

 paired conical shaped structure. The base just projects 

 into the posterior part of the body cavity; the apex pro- 

 jects backwards towards the tail, lying between the 

 haemal spines and the muscles of the trunk. The oviducts 

 are extremely difficult to dissect and do not open exter- 

 nally. In the following year the organ rapidly develops. 

 In male Plaice of the same size the testes are paired 

 ridges of the posterior body wall projecting forwards into 

 the body cavity, but having no extension backwards as in 

 the case of the ovaries. 



The Female organs. — Fig. 20 represents the condition 

 of the ovary in a mature and nearly ripe Plaice. The 

 specimen figured was captured in December. The ovary 

 is seen to project far forward into the body cavity, dis- 

 placing various organs from their normal positions. Part 

 of the posterior extension of the organ is indicated in the 

 figure ; it really extends backwards to near the root of the 

 tail. Its posterior portion lies along the external surface 

 of the haemal spines, and is only separated from these by 

 loose: areolar tissue. The overlying muscles of the trunk 

 are very thin, and occasionally the ovary appears to be 

 covered only by integument and connective tissue. In 

 this condition it can be felt externally as a hard pad lying 

 on either side of the ventral portion of the body behind 

 the anus. The ovary of the ocular side appears to be, 

 sometimes at least, more strongly developed than that of 

 the eyeless side. 



