77/(' rroditclri'lly of Fish Food in Oneida Lake 20C) 



\ui]; to llic tola! amount of food available in Danish marine 

 waters. I'Vjr this purpose he caui^ht numbers of fish at dif- 

 ferent times of the day to see if there was a difference in the 

 (|uantity of food l)y nij^ht or by (l;iy. lie found that in the 

 early mornini^- most of the dii;cslive tracts were empty, but 

 at ]o o'clock A. M. most tracts wcie hlled. hish caught in the 

 afternof)n and evening until 7 i'. M. were also hlled with food. 

 From these facts I'etersen concluded that the digestive tract 

 WAS emptied once in the course oi 24 hours ('11, pp. 63-66). 

 Petersen's table (No. 53) is re[)roducod below: 



'rAHi.K No. 5,v Food of Pl.-vice Eaten in 24 Hours 



I'legvad has also investigated the question of the rate of 

 digestion in some of the fish of European marine waters. He 

 e.xamined ('16, pp. 35-37) 290 young specimens of a common 

 Cioby {iiohiifs rnlhcnsparri luiphrasen), a small marine fish 

 abundant in' the seas of northern Europe, at different hours of 

 the day on six different da}s in August and September. He 

 found that the food passed through the alimentary canal in 

 about six hours. Most of these fish appeared to feed during 

 the day time, the stomach being generally empty in the morn- 

 ing. In 'fable No. 54 the data u[)on which Pdegvad based his 

 conclusions are given. 



The Plaice and (ioby are marine fishes and, therefore, the 

 experiments of Petersen and of Blegvad cpioted above are 

 mainly suggestive in the ])resent connection. The difference 



