GENERAL REMARKS ON THE EGGS OF MARINE FISHES. 25 



case of the stickleback and its nest is an example in fresh water. 

 The fifteen-spined stickleback, gunnel, bimaculated sucker, 

 pipe-fishes, and lumpsucker are instances in the sea, the male 

 in the majority acting as the guardian. 



Whether the eggs of the wolf-fish (cat-fish) are at first fixed 

 to the bottom is unknown, but they form bulky masses 

 occasionally about a foot square, which are carried by the tides 

 into neighbouring areas. These masses are only a little 

 heavier than the water, and hence are readily wafted about 

 by currents. 



In other groups of animals, for instance the cuttle-fishes, 

 the same divisions occur in the eggs, some forming demersal 

 masses of various shapes, or being fixed to foreign bodies, while 

 others are pelagic. The majority of them, however, are demersal. 



Summing up then the general facts concerning the early 

 development of the food-fishes we find three leading types : 



A. That of the cartilaginous fishes with a minimum 

 number of large eggs, with a maximum amount of ' protection ' 

 (in the widest sense) in the way of thick capsule, and great 

 quantity of yolk, and a lengthened period of incubation so 

 that the young is considerably developed before hatching. 



B. That of the bony fishes with demersal eggs. 



An abundance of small eggs, with a varying amount of 

 protection, either by a tough capsule, concealment, colour and 

 position or by direct contiguity of the parent, more or less 

 close, and a fairly long period of incubation. 



C. That of the bony fishes with pelagic eggs. 



An immense number of very small eggs, with small quantity 

 of yolk, an objective protection by translucent appearance but 

 no parental protection whatever, a rapid period of incubation 

 and more or less helpless larval form. 



Stages after hatching. The later stages of development are 

 usually classified for convenience into Larval, Post-larval and 

 Adolescent. The larval stage extends from the period of 

 hatching till the complete absorption of the yolk-sac, which 

 in larval forms hangs like a large ' hernia ' from the ventral 

 surface of the newly hatched fish. During this period its 

 movements are greatly hampered by this large sac of mi- 



