16 GENERAL REMARKS ON THE EGGS OF MARINE FISHES. 



enormous quantities, as G. 0. Sars, for instance, describes ofif 

 Lofoten, may be beached by the tide, but such has never been 

 observed in our country, probably because the fishes are fewer 

 and the spawning-areas at a greater distance from the shore. 

 Again, these small glassy spheres are often engulphed by such 

 pelagic fishes as the herring, when swallowing their crustacean 

 prey, as many as twenty having been observed in good condition 

 in the stomach of a single example. They may also be destroyed 

 by the small crustaceans (shrimp-like forms) amongst which 

 they float, as well as by other invertebrates which form the 

 pelagic fauna usually so abundant in our waters. 



The third and last proposition, viz. that the pelagic con- 

 dition of the eggs appears to have played an important part 

 in the preservation of the various food-fishes, offers many points 

 for remark. In the first place, fishes which are endowed with 

 this property do not shed all the eggs at once, but only a portion 

 of the roe ripens at a given time and the eggs pass externally, 

 and so at intervals until all the mature eggs are discharged. 

 Several weeks would thus appear to elapse in certain cases 

 before an individual ceases to spawn. The effect of this 

 condition is twofold, viz. to give a much wider area for 

 distribution and a series of gradations in the growth of the 

 young of the same fish. In this way a succession of larval 

 fishes is liberated, and time is afforded for those of one stage 

 to disappear from the surface before those of the succeeding 

 stage take their places. Moreover, it is evident that even 

 if circumstances were unfavourable for the vitality of one 

 series of such ova, they would rarely be unfavourable for all. 

 Such eggs are therefore in a different category from those of 

 the salmon and wolf-fish in which the contents of the ovaries 

 ripen simultaneously and are discharged about the same time. 

 On the whole, it would seem that the advantage is on the side 

 of the minute translucent pelagic eggs, which under the varied 

 circumstances of their periodic discharge seem to be placed in 

 favourable conditions. Again, pelagic eggs as a rule are small, 

 so that instead of the 28,000 or so of ova of the salmon, there 

 are 6 — 9 million eggs in the cod, and a still larger number in 

 the turbot. 



