CHAPTEE XII. 



OEGANS OF EEPRODUCTION. 



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 fem'ale ; or the organ of one. or bo'th 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 dilfited 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 suflicient for effectual im- 

 pregnation of a number of ova dispersed in a considerable 

 quantity of water; circumstances which render artificial 

 impregnation more practicable than in any other class of 

 animals. , 



In SraTichiostoma the generative organs occupy the ventral 

 side of the abdominal cavity, into which they discharge their 

 contents. No ducts are developed in either sex. 



