GENERAL REMARKS ON THE EGGS OF MARINE FISHES. 23 



compared to the milt than is the case in ' demersal ' fishes. In 

 the cases where there is not a great disproportion between the 

 relative number of the sexes, as, for example, the cod, the 

 disparity in the relative sizes of the organs is more marked, 

 always to the disadvantage of the male sex. 



Demersal eggs. In the fishes of ' demersal ' habit the males 

 are usually in excess of the females, which also probably results 

 from the fact that the process of fertilization in these fishes 

 is not assisted by physical factors, as in the 'pelagic' fishes. 

 In the latter the micropyle or minute aperture of the egg 

 is downwards, and the ' milt ' being specifically lighter than the 

 water passes upwards and meets the egg as it slowly ascends 

 through the mid-water. 



In the ' demersal ' species the batches of eggs are close 

 together and are not so readily accessible to the male element. 

 In this category are most fresh water fishes (except the shad), 

 the eggs being deposited on the bottom like those of the 

 salmon, attached to foreign bodies like those of the sparling, or 

 to water-plants as in the carp and the pike. These fresh water 

 fishes are held to be descended from marine ancestors which had 

 already acquired a demersal spawning habit. There are 

 obviously many physical difficulties in the way of a fresh water 

 fish reproducing itself by buoyant eggs. (See ' Flounder ' and 

 ' Eel.') Amongst the marine fishes demersal eggs occur — in 

 the herring, wolf-fish, shanny, various suckers, gobies, armed 

 bull-head, sea-scorpions (Gotti), ballan wrasse, fifteen-spined 

 stickleback, gunnel and others. 



These ' demersal ' eggs are so called because they are de- 

 posited by the mother upon the bed of the ocean, and in many 

 cases some amount of regard for concealment is shown in the se- 

 lection of a site for the deposition of them. As we might expect, 

 therefore, these eggs are not usually by any means so numerous 

 and are not so translucent, but often have a typical colour and 

 are opaque. They are usually deposited in masses of scores 

 or hundreds attached to weeds, shells, or rocks, where the 

 development takes place up to the hatching stage, often under 

 the direct protection of the male, as in the case of the stickle- 

 back and lumpsucker. If, as already indicated, we separate 



