CHAPTEE XII. 



ORGANS OF REPRODUCTION. 



All fishes are dioecious, or of distinct sex. Instances of 

 so-called hermaphroditism are, with the exception of Serranus, 

 abnormal individual peculiarities, and have been observed in 

 the Cod-fish, some Pleuronectidse, and in the Herring. Either 

 the generative organ of one side was found to be male, that 

 of the other female ; or the organ of one or both sides was 

 observed to have been developed partly into an ovary partly 

 into a testicle. In the European species of Serranus a tes- 

 ticle-like body is attached to the lower part of the ovary; 

 but many specimens of this genus are undoubtedly males, 

 having normally developed testicles only. 



The majority of fishes are oviparous, comparatively few 

 viviparous ; the embryos being developed either in the ova- 

 rium or in some dilated portion of the oviduct. In vivi- 

 parous fishes actual copulation takes place, and the males of 

 most of them are provided with copulatory or intromittent 

 organs. In oviparous fishes the generative products are, 

 during sexual excitement, discharged into the water, a very 

 small quantity of semen being sufficient for effectual im- 

 pregnation of a number of ova dispersed in a considerable 

 quantity of water; circumstances which render artifieial 

 impregnation more practicable than in any other class of 

 animals. 



In BrancMostoma the generative organs occupy the ventral 

 side of the abdominal cavity, into which they discharge their 

 contents. No ducts are developed in either sex. 



