276 PROCEEDINGS OF THE ACADEMY OF [1896. 



THE PLANKTONOKRIT, A CENTRIFUGAL APPARATUS FOR THE 



VOLUMETRIC ESTIMATION OF THE FOOD-SUPPLY OF 



OYSTERS AND OTHER AQUATIC ANIMALS. 



BY CHARLES 8, DOLLEY, M. D. 



To Dr. Victor Hensen of Kiel is due the credit of being the first 

 to insist upon the importance of a quantitative determination of the 

 primitive food supply of marine animals. 



In place of the terms "Auftrieb" and " pelagische Mulder " (pel- 

 agic tow-stuff) introduced by Johannes Miiller, and commonly em- 

 ployed by zoologists for nearly half a century, Hensen substituted 

 the more comprehensive term, plankton,^ to include all those free- 

 swimming, or drifting organisms which make up the fauna and 

 flora of the sea. As the result of the initiative taken by Hensen 

 and based largely upon the investigation conducted in the North 

 Sea and Atlantic Ocean under his leadership, there has been devel- 

 oped in less than a decade, one of the most important departments 

 of biological science, to which Haeckel has applied the term plank- 

 tology. Biologists interested in the practical solution of the diffi- 

 culties met with in the preservation and propagation of the food 

 supply of Man, as found in ocean and lake, bay and river, were 

 quick to recognize the importance of planktonic studies ; and the 

 broad considerations of the physiologist, concerning the cycle of 

 matter in the sea, have led to narrower, but, nevertheless, exceed- 

 ingly important studies regarding the source, character and quan- 

 tity of the food supply of edible fishes and mollusks. 



It is each year becoming more evident to the fish and oyster cul- 

 turist that he has before him a problem of very considerable com- 

 plexity. He is awakening to the fact that it is not sufficient that 

 he should be able to hatch out and liberate millions of young fish 

 fry, or plant thousands of bushels of oyster spat, but that he must 

 base his culture experiments upon a thorough knowledge of the 

 conditions affecting the survival and growth of the planted forms. 



To the very imperfect knowledge of fish culturists and oyster plant- 

 ers, may be largely attributed the fact that American oysters have for 



1 _ 



■:lay/.T6<i, wandering, roaming. 



