Pelagic Fauna of our Shores. 141 



life, and tliej sometimes slum the upper waters for length- 

 ened periods, being found only in the lower stratum, both by 

 night and bj day. As a rule, however, voyagers have cap- 

 tured them most abundantly in the tow-nets in the evening. 

 D'Orbigny's pleasant but fanciful description of the habits of 

 these forms is inadequate to explain such phenomena. Lastly, 

 the larvEe of the cuttlefishes, which on the eastern coast deposit 

 their eggs on the bottom, shoot upward into the water on 

 emergence, and are as lively as the adults in ordinary circum- 

 stances are sluggish. 



From the foregoing brief and somewhat imperfect summary 

 it will be apparent that the animals which constitute the 

 invertebrate pelagic fauna are both numerous and varied ; 

 and as the representatives of almost every group are more or 

 less adapted to form the food of other types or even of its 

 own, it follows that there is abundance of nourishment of this 

 kind in the inshore and neighbouring waters, as well as in 

 many parts of the open sea. 



Further, the young food-fishes themselves form important 

 members of the pelagic fauna. Almost every food-fish, 

 indeed, passes through the pelagic phase, either temporarily 

 as a pelagic form or remaining so throughout life, like the 

 herring, the pilchard, and the mackerel. It is true the ova of 

 the herring are deposited on and glued to the bottom ; but the 

 larval fish rises, as soon as it gains sufiicient strength, to the 

 upper regions of the water. Again, with the exception just 

 mentioned and a few others, the majority of the Teleostean 

 food-fishes produce ova which mount in still water to the 

 surface or near it in more restless seas. The young are there 

 hatched in a very incomplete state, generally without a mouth, 

 and subsist for some days on the store of nourishment in the 

 small yolk-sac *. They are carried about in a helpless con- 

 dition by the surface-currents, but probably do not proceed 

 very far from the area in which they emerged. Before the 

 absorption of the yolk-sac the mouth has formed and the 

 little fish, already full of activity, is in a condition to prey on 

 the more minute forms around it. 



Introduced into life from pelagic eggs and in the midst of 

 pelagic surroundings, the young of the food-fishes much 

 resemble each other in general outline, though there are 

 certain characters, chiefly specks of pigment, which enable 

 the zoologist to discriminate them. Each has a marginal fin 

 commencing behind the nape of the neck and running verti- 

 cally to the tail, which it includes, and then forward along 



* Vide E. E. Prince, " Development of Food-Fishes," Ann. & Mag. 

 Nat. Hist., May and August 1886, 



