VITALITY OF, MARINE ANIMALS. 87 



Second. — Those that will . survive simple aeration of the water in 

 which they are placed, the water itself not being changed, usually, but 

 only added to to make up for evaporation. To this class belong crabs 

 and other small animals that are just about to lay their eggs, together 

 .with young of all sor.ts in their swimming or larval stages. In these 

 cases, .however, the "injector" is often made use of. This consists of a 

 spindle-shaped chamber of brass, with external ppenings, so that, as the 

 stream of water pas.ses through, it sucks into its current a quantity of air 

 which goes to the jar mingled with the stream. This little injector is, in 

 fact, a miniature Catalan blow-pipe, being constructed on exactly the same 

 principle as that which supplies the tweers of a blast-furnace. It is a con- 

 trivance of great value in the laboratory. 



.Third. — The morsels of almost invisible life, too delicate to resist 

 ever so feeble a current, and too volatile and minute not to escape in an 

 overflow, however well guarded. To the receptacle of these only a very 

 gentle, though unremitting supply of air can be given, while the water 

 must frequently be changed by cautious dipping out and pouring in 

 by hand, a trifle at a time. No mother attends to her infant with more 

 tender and scrupulous care than the zoologist to these babies of the sea. 



And what are they ? Eggs of fishes, mollusks, crustaceans, and radi- 

 ates ; embryos of similar animals and of jelly-fishes — filmy, fragile, nine- 

 teen-twentieths water — which would perish under the slightest injury, and 

 can only be kept alive by the greatest painstaking. That Mr. Agassiz 

 has been successful beyond all precedent in preserving these excessively 

 delicate pelagic forms in his laboratory, shows how admirable are all his 

 methods and appliances to reproduce the most healthy conditions of nat- 

 ure. It was no mean triumph, for instance, to have reared those young 

 flounders and goose-fish from eggs scooped up in the open sea, and to 

 have kept them all summer, while he noted and sketched the various 

 aspects, of thejr growth. But the highest surety of the suitability of 

 his arrangements was afforded when the vapory, translucent siphono- 

 phores, in which no one before had been able to maintain vitality for 

 -more than two or three hours, lived contentedly in their glass prison last 

 summer during fifteen days. One highly favorable circumstance, no 

 doubt, is that the temperature of the water in the Newport laboratory 

 is cooler than that of the open sea. Heated by the ever-present Gulf 

 Stream, the ocean in summer rises to a warmth of seventy-six or seventy- 

 seven degrees Fahrenheit; by the time it has passed through the pipes 

 and the shaded cistern this water has been considerably cooled down, and 

 -remains at a lower temperature than that of the native element from 



