78 MARK1 TAHLE BRITISH MARINE FISHES CHAP. 



not only important but attractive. The explanations offered 

 here must not be considered as by any means complete or final, 

 but merely as conclusions suggested by our present imperfect 

 knowledge. 



In the herring it has been found that there is very little 

 difference between the weights of the ripe milts and ripe roes, and 

 that little is on the side of the milts. In the cod the ovaries 

 were found to weigh between two and three times as much as the 

 milts. In the plaice the roes were about seventeen to twenty 

 times as heavy as the milts, in the flounder about forty times, 

 while in the sole the inferiority of the milt in size reaches its 

 extreme. The obvious difference between the herring and the 

 other fishes mentioned is that the spawn of the former is attached 

 to solid objects while the eggs of the latter become free and 

 separate in the water. Milt when shed into the sea-water diffuses 

 through a large quantity of it quickly and so becomes much 

 diluted, and as the water of the sea is usually moving in the tidal 

 currents in one direction or another the milt is also carried away 

 at a certain rate from the place where it is shed. From these 

 causes a considerable proportion of the milt shed by male 

 herrings where the females are spawning has no chance of 

 coming into contact with the eggs at all, but is wasted. It may 

 be said that, while the eggs of some fishes are fixed and those of 

 others buoyant, the milt is always buoyant. We have here an 

 obvious reason why the herring should require a large quantity 

 of milt, and we may conclude that where the milts are as large 

 as the roes a great waste of the male generative material occurs 

 in the process of spawning. On the other hand in cases where 

 the eggs are buoyant and free they disperse in the water and 

 are carried by currents at the same rate as the milt, and the 

 result is the same as though both were confined in a small 

 quantity of still water. There is consequently very little waste 

 of milt, and a smaller quantity suffices to ensure fertilisation. 

 In the cat-fish, which like the herring produces fixed eggs, 

 according to Dr. Fulton's figures as given above the males arc in 

 number in excess of the females in the proportion of 100 to 79, 

 but concerning the size of the ripe milts we have no observations. 

 The males of the lump-sucker, of which the spawn is also fixed, 

 arc said to be much more numerous than the females, althoti-h 

 considerably smaller. But here we have to consider not merely 



