REPORT OF COMMISSIONERS OF INLAND FISHERIES. 85 



vision for keeping it in suspension, in which condition only would it 

 be available. 



REQUIREMENTS SATISFIED. 



After the first step was taken and the excellent results of rearing 

 bottom-living animals in native water was recognized, it seemed most 

 desirable to follow up the advantage gained in the rearing of other 

 forms by extending and developing the procedure so that it would be 

 applicable to pelagic fry. Fortunately we were able to hit upon a 

 method which solved at once all the main difficulties arising from the 

 peculiarities of pelagic existence of larvae and other free-swimming 

 animals. This method consists essentially of creating and maintain- 

 ing within an inclosure of "native" water a gentle upward swirling 

 current. It obviates the several difficulties which we have enumera- 

 ated as peculiar to pelagic fry in the following ways: 



It effectually prevents the crowding of the fry to one wall of the 

 car, for the force of the current carries them round and round con- 

 tinuously, nor can they work their way to the bottom, for the current 

 has an upward as well as a rotary direction. Even the cannibalistic 

 propensities, which are so pronounced in the larval stages of lobsters 

 and some other animals, are rendered innocuous to a great extent by 

 the forced separation of the fry and are mitigated by the availability 

 of other food. 



The current being wholly internal, and its main component circular 

 in its course, it does not force the fry strongly to one side nor allow 

 them to remain in one place as does the tidal current passing through 

 the inclosure. The pressure of the current against the sides varies, 

 of course, with the rapidity with which the outside water is drawn 

 into the car, with the extent of the area through which the water can 

 pass out, and with the rapidity of the current. Since any or all of these 

 factors can readily be controlled there is no difficulty in obtaining a 

 proper adjustment of current for the requirements of particular 

 cases. 



