34 THE COMMERCIAL SEA FISHES OF 



canal, or with a simple duct ; a partial oviduct united to 

 the ureter, but not continuous with the ovary ; or a testis 

 and ovary having a complex duct distinct from the ureter. 

 In short, the products of the reproductive organs may be 

 set free in the peritoneal cavity, becoming discharged ex- 

 ternally by the abdominal pore or pores ; or the products 

 may be taken up by the open mouths of the fallopian 

 tubes, or proper ducts may conduct them to their outlet 

 The claspers, as seen in the male sharks, rays, and their 

 allies, are really intromittent organs. In the pipe-fishes 

 other accessory organs exist, as the sub-caudal skinny 

 pouch in the males of some forms, or the sub-abdominal 

 pouch in the male horse fishes. 



Among bony fishes breeding occurs in one of the fol- 

 lowing plans ; (i) the eggs are hatched within the female 

 organs, as seen in the viviparous blenny ; or (2) as in the 

 majority of these fishes, having been extruded as hard 

 roe, they are subsequently fertilised by the milt of the 

 male, which comes into contact with them when in the 

 water. 



There is much which still remains to be ascertained 

 respecting the breeding of fishes in the sea. Some forms, 

 as the herring, deposit eggs which sink to the bottom, and 

 attach themselves to contiguous substances. Others, like 

 the mackerel, pilchard, and cod, float ; or others, like some 

 of the flat fishes, have their specific gravity so nearly 

 similar to that of the sea, that it requires the agitation of 

 the waves to prevent them from subsiding. Most of the 

 sea forms which are of commercial importance migrate at 

 breeding time towards localities most suitable for the 

 reception of their eggs, generally seeking banks, or being 

 found nearer in shore, or in shallower waters, than those 

 they generally inhabit ; while in the gar-fish (Belone) and 



