12 GENERAL REMARKS ON THE EGGS OF MARINE EISHES. 



we are at once struck by a great contrast between their 

 development and that of the cartilaginous fishes. 



The egg of the cod is very small, and is surrounded by 

 a delicate capsule or membrane. The main part of its contents 

 consists of a mass of nutritious yolk, ready-prepared by the 

 parent for the use of the little embryo, and as the egg is 

 entirely left to shift for itself, the numbers destroyed by 

 voracious enemies, and still more by adverse physical condi- 

 tions', must be very great indeed. Hence, in order to maintain 

 the normal number of the species, the cod lays an enormous 

 number of eggs, one female laying several millions. The same 

 carelessness as regards its young is exemplified by these fishes 

 beyond the egg-stage. The young cod escapes from its egg 

 at a much earlier stage of development than the young skate, 

 and is hence in a much more helpless condition, larval cod 

 being at first unable to look after themselves, and at this 

 stage also the mortality of the little fishes must be very high. 

 In this respect the cod is an extreme type of the bony fishes, 

 and in such a very large group of animals there are endless 

 variations both in the character of eggs and in the mode of 

 development. 



Gener-al Reuim^ks on Eggs. In general form the eggs of 

 the ordinary food-fishes- are circular. On deposition they are 

 usually invested by a single layer (capsule or zona radiata). 

 But some are ovoid or fusiform, as in the case of the anchovy 

 and goby, and others have long filaments attached to the 

 capsule, as in the gar-pike, saury-pike, flying-fish and sparling, 

 these filaments occasionally fixing them to foreign structures. 

 Amongst other interesting types are the large eggs of the stickle- 

 back, the wolf-fish and the salmon-tribe. These eggs, however, 

 are surpassed in size by those of the Siluroid genus Arius, found 

 both in the Old World and the New (Ceylon and Guiana), 

 the eggs of which are somewhat larger than a pea (viz. 5 

 to 10 mm.). This is not the only remarkable feature in these 

 fishes, for as Urs Gunther and Wyman and Prof. Sir William 



1 "Effect of pelagic spawning habit upon life-histories of food-fislies.'' 

 Beport Brit. Assoc. 1896. A. T. Masterman. 



•■' Vide Prof. Mcintosh, Nature, April 9, 1885, Vol. 31, pp. 534 and 555. 



