A STUDY OF TWIN LAKES, COLORADO. 175 



upon these snail 1 crustaceans. The great majority of the adult females had either 

 eggs or developing embryos in their brood chambers. Whether the eggs are 

 destroyed during their passage through the alimentary canal or not is still an open 

 question. FriS and Vavra (1894) found thai summer eggs sometimes pass through 

 the canal undigested, Imt they did not determine whether these eggs had. lost their 

 vital power. Steuer (1901), however, raised a Ceriodaphnia from an ephippium 

 which was taken from the intestine of a fish. But, even if the majority of the eggs 

 eseaped digestion and developed afterwards, it hardly seems probable that the 

 embryos escaped also, and they alone represented a very large additional loss. 



Steuer (1901) calls attention to the likelihood of overestimating the value of 

 Entomostraca as a direct source of food for fishes. He thinks that, in very many 

 cases, they enter the digestive tract of the fish only indirectly; that i~. after being 

 eaten by some animal which is in turn eaten by the fish. There was no room for 

 doubt as to their being eaten directly by the trout in these cases. In a number of 

 instances there was nothing else in the stomachs; and in stomachs which contained 

 additional food the additional food in most instances consisted of insects that had 

 accidentally fallen into the water, and these of course had not been feeding on 

 Entomostraca. 



BIBLIOGRAPHY. 



Abbott, C. C. 1878. Notes on some fishes of the Delaware River. Report U.S. Fish Commission, 



1875 -76 I L878), p. 825-845. 

 Baikd, Spencee F. 



1s7l\ The food of the sea-herring. Annual Record of Science and Industry for 1871, p. 208-210. 



1872. Food' for young trout, [bid., 1871, p. 217. 



1872. Nutrition of young fish in hatching establishments. Ibid., 1*71, p. 350-352. 



1873. Food of shad. Ibid., 1872, p. 426. 



1874. F I of the basking shark. Ibid., 1873, p. 328-329. 1874. 



1S74. F 1 for diminutive trout. Ibid., 1873, p. 447. 



1874. Increase in the growth of trout, [bid., 1*7:;. p. 148. 



1875. Food of the shad, [bid., 1874, p. 310-311. 



1876. Food for trout, [bid., 1875, p. *33 434. 



Bairh, W. 1857. Notes on tin- food of some fresh-water fishes, re particularly the vendace and 



trout. Edinburgh Philosophical Journal, n.s., vol. vi, 1857, p. 17 24. 

 Barfubth, D. 1876. UeberNahrungund LebensweisederSalme,Forellen,und Maifische. Inaugural 

 dissertation. II p. Translated by 0. Jacobson, in Report U.S. Fish Commission, 1873-74and 

 1874-75 i L876), p. 7:;:. 759. 

 Beardsley, A. E. 1902. Notes on Colorado Entomostraca. Transactions American Microscopical 



Society, vol. xxm, p. 41-4S. 1902. 

 Birge, E. A. 1897. Plankton studies on Lake Mendota (Hi. Transactions Wisconsin Academy of 

 Sciences, Arts, and Letters, vol. H, 1897, p. 274-448, 28 pi. 



1904. The thermocline and its biological significance. Transactions A rican Microscopical 



Society, vol. xxv, 1904, p. 5-33, 2 pi. 

 Brook, i . 



1886. Preliminary account of the food of the haddock, fourth Annual Report of Fishery Board 



for Scotland, app. F, no. 6, p. 128-134. 1886. 

 1886a. Preliminary report on the food of the cod. Fourth Annual Report of Fishery Board for 

 Scotland, app. F, no. 6, p. l:'.4-147. Is ; 



1887. Notes on the food of young Gadidae. Fifth Annual Report of Fishery Board for Scotland, 



app F, no. 10, p. 326-327. 



Brook, G., and Cal'jerwood, W. L. 1886. Report on the i 1 of the herring. Fourth Annual 



Report of Fishery Board for Scotland, app. F, no. 6, p. 102-128. 1886. 



