FINGER LAKES OF NEW YORK. 



243 



we may say that the average difTerence for the year would be substantially fourfold. 

 The differences are much greater in the Finger Lakes, ranging from about fourteenfold 

 in Seneca Lake to almost thirty-fivefold in Canandaigua lake. (See Table 22, p. 250.) 



The dry organic matter of the grass was made up of about 25.4 per cent crude 

 protein, 4.7 per cent ether extract, while the remainder consisted of carbohydrates. 

 The plankton of Lake Mendota, however, was distinctly richer in nitrogenous material 

 and in fats; the average for the crude protein was 45.1 per cent of the dry organic 

 matter and for the ether extract 8 per cent. 



Attention should also be called to the fact that the plankton does not represent 

 all of the food material that is produced by a lake; the bottom fauna and the large 

 aquatic plants growing in the shallower water make notable contributions to this mate- 

 rial. The quantity of plankton is not as large per unit of surface in the shallower water 

 as it is in the deeper water, but the larger bottom population in the former region tends 

 to counterbalance this deficiency when the question of the total production is con- 

 sidered. 



PLANKTON TABLES. 



Tables 17 and 18 show the vertical distribution of the various organisms consti- 

 tuting the net plankton, giving the number of individuals per cubic meter of water in 

 the different strata. The members grouped in the different columns are indicated as 

 follows: 



Cladocera. — B=Bosmina, C=Ceriodaphnia, D=Daphnia, Di=Diaphanosoma, L=Leptodora, 

 P = Polyphemus. 



CoPEPODA. — C=Cyclops, D=Diaptomus, E=Epischura, L=Liinnocalanus. 



Naupui. 



RoTiFERA. — A=Asplanchna, A.<i.=Anitraea aculeata, A.c.=Anuraea cochlearis, C=Conochilu3, 

 N=Notholca, P=PoIyarthra, Pl=Ploesoma, R=Rattulus, S=Synchaeta, T=Triarthra. 



Protozoa. — A=Actmosphaerium, C=Ceratium, D=Dinobryon, E=Epistylis, M=Mallomonas, 

 U=Uroglena, V=Vorticella. 



Green and blue-green alg^e. — An=Anabaena, Ap=Aphanocapsa, Coe=Coelosphaerium, 

 G=Gloeocapsa, L=Lyngbya, M=Microcystis, 0=Oscillatoria, S=Staurastruni. 



Diatoms. — A=Asterionella, F=FragiIaria, M=Melosira, S=Synedra, T=Tabellaria. 



Table 17. — Analysis of Net Plankton, 1918. 

 canandaigua lake. july 27. 1918. 



