144 Prof. M'Intosh on the 



On glancing at the various forms of pelagic animals it is found 

 that both those which are temporarili/ and those whicli are 

 permane72thj pelagic are important factors in the food of fishes. 

 The temporarily pelagic include such forms as larval stages 

 of sponges, hydromedusaj, and larval coelenterates, larval 

 stages of starfislies, annelids, crustaceans, moUuscoids, and 

 mollusks, as well as the ova and young of fishes. The other 

 or permanently pelagic group may be represented by the 

 ctenophores, certain medusa, copepods, schizopods, and other 

 crustaceans, Tomopteris and other annelids, pteropods, certain 

 cephalopods, and fishes. Some of the small forms, such as 

 diatoms. Infusoria, larval meduste, and starfishes, are rare in 

 the stomachs of the minute food-fishes ; but still the first two 

 are occasionally found there. Moreover tliey are devoured 

 by the crustaceans and mollusks, which subsequently nourish 

 the fishes. Two groups especially stand out as universally 

 distributed constituents of the food of the young fishes, viz. the 

 crustaceans and the mollusks. The former is by far the most 

 general at a very early stage ; the latter is more character- 

 istic of the later stages. 



It is an interesting fact that at the time when the pelagic 

 ova give birth to the young food-fishes the ocean especially 

 abounds with the minute forms of the Crustacea, such as 

 young copepods and the larvse of other groups *. As soon as 

 the yolk-sac is absorbed, and even before it is wholly absorbed, 

 the most minute (almost microscopic) specimens of such crus- 

 taceans are found in the stomachs of the little fishes. More- 

 over this food is almost universal, for not only the young of 

 the round and flat fishes (which keep up the relish for crus- 

 taceans in adult life), but the young of such forms as Cyclo- 

 pterus lumpus, which, when full-grown, rarely feeds on 

 crustaceans, and the young of Loj^hius piscatonus, which is 

 strictly a destroyer of fishes in after life, follow the same 

 habit. Nor is this food confined to their sojourn near the 

 surface. As they grow older they descend to the lower 

 water, where the same nourishment abounds, and there the 

 young cod, haddock, whiting, ling, gurnard, and others disport 

 themselves in the unceasing pursuit. The young flat-fishes 

 accompany them, still swimming on edge and with an eye on 

 each side, but being readily recognized by certain peculiarities, 

 amongst which is the greater depth of the body. The nature 

 of the food in many cases is indeed recognized with tolerable 

 certainty at first sight, since in the more advanced larvjB the 

 crustaceans (e. g. Galanus Jtnmarcliicus) tint the under surface 

 of the translucent abdomen of a delicate pinkish hue. 



* In this respect there is a parallelism with the atmosphere aud insect- 

 life in summer and autumn. 



