THE PELAGIC FAUNA AND FLORA. 



179 



The customary method of collecting* these pelagic animals 

 fi-om the surface is by means of a tow-net, dragged behind a 

 boat as it moves slowly through the water, or hung from the 

 sides of the steamer in any w^eather which allows the handling 

 of a trawl or di-edge. The contents of the net are emptied 

 into glass jars, and carefully examined. The larger speci- 

 mens of fishes, of annelids, of crustaceans, of mollusks, and 

 of coelenterates, visible to the naked eye, are of course in 

 better condition when collected with a hand-net. The smaller 

 fry alone survive the 

 packing which they 

 get at the bottom of 

 the tow - net. Fre- 

 quent examination of 

 the net is important in order to 

 obtain in proper condition the 

 more delicate pelagic animals. In 

 many cases the contents of the 

 tow-net consist chiefly of pelagic 

 Crustacea, among which the pro- 

 minent types are the Calani and 

 other pelagic copepods. (Fig. 

 84.) The many species, of Mysis 

 (Fig. 85), regular tramps of the 

 sea, are with the Calani the great 

 marauders of the pelagic fauna, 

 attacking at once any of the 

 larger animals which show the 

 least signs of decay .^ . ^^ 85. -Mysis. f. 



1 Around our coasts and in the Gulf of Mexico and the Caribbean, small Hemi- 

 ptera (Halobates) (Fig. 123) are not 

 unfrequently met, skimming over the 

 surface at a considerable distance from 

 the coast. The larva of a species of 

 fly (Chironoinus) is quite common off 

 shore fi-om our northern coasts. The 

 " Challenger " found the pelagic Ha- 

 lobates very abundant in certain regions 



rtf +Vio Pa^ifif Fiff. 123. — Halobates wiillerstorffi. 



ot tne racmc. -s ^ (ChaU.) 



