FINGER LAKES OF NEW YORK. 237 



In Seneca Lake Ceratium and Dinobryon constituted the protozoan population. 

 A relatively small number of the latter was noted in the 5 to 10 m. stratum. Ceratium 

 was distributed through the upper 20 m. but was most abundant in the upper 5 m. 



The rotifer population was largest in Cayuga Lake and smallest in Canandaigua 

 Lake in 1918. In the latter lake rotifers were most numerous in the upper 10 m. while 

 in Cayuga and Seneca Lakes the largest number was found in the upper 15 m. 



The maximum number of individuals in the rotifer group was noted for Synchaeta 

 in Cayuga Lake, where it reached 44,700 per cubic meter of water in the 10 to 15 m. 

 stratum; the average number in the upper 15 m. was 35,950 individuals. This form 

 was not found in the other two lakes. 



Polyarthra was noted in the catches from each of the three lakes in 1918, but it 

 was most numerous in Cayuga Lake, reaching a maximum of 21,000 individuals per 

 cubic meter in the 5 to 10 m. stratum. The maximum number in this lake in 1910 

 was a little more than ten times as large as this. 



Conochilus was also found in the catches from each of the three lakes, but it, too, 

 was most abundant in Cayuga Lake, reaching a maximum of 33,750 per cubic meter 

 in the o to 5 m. stratum. 



A few individuals of Anuraea cochlearis were found in the upper water of Canan- 

 daigua and Seneca Lakes, but this form also was distinctly more numerous in Cayuga 

 Lake. The catches from Canandaigua Lake contained a few specimens of Noiholca 

 longispina, and the material from Cayuga Lake showed the presence of a few individ- 

 uals of Asplanchna and Ploesoma in the upper water. 



The rotifer population of Canandaigua Lake was substantially the same in 1918 

 as in 1910. (See Tables 17 and 18.) In Cayuga Lake Polyarthra was not nearly as 

 abundant in 191 8 as in 19 10, but the other forms were more numerous, in general, in 

 the former year. In Seneca Lake not so many forms were represented in 1918 as in 

 19 10, but those that were present were more numerous, so that the total rotifer popu- 

 lation was somewhat greater in the former year. 



In Green Lake the rotifers were more abundant than in Canandaigua Lake, but 

 they were not as numerous as in Cayuga Lake ; the number in the upper 20 m. was 

 substantially the same as that of this stratum in Seneca Lake. 



Copepod nauplii were most abundant in the upper 20 m. or 30 m. of each lake, 

 but they were present in the lower strata also. A larger number was found in Seneca 

 Lake than in the other two lakes and the number in Seneca Lake was larger in 19 18 than 

 in 1 9 10. In the other two lakes they were more numerous in the latter than in the 

 former year. They were more abundant in Green Lake than in any of the Finger Lakes. 



Three genera of copepods were represented in the net catches from each of the 

 three Finger Lakes, namely, Cyclops, Diaptomus, and Limnocalanus ; while a fourth, 

 Epischura, appeared in the 5 to 10 m. stratum of Canandaigua Lake. By far the greater 

 portion of the copepod population consisted of Cyclops and Diaptomus, the former 

 being numerically greater than the latter in each of the lakes. Both of these forms 

 were more abundant in Seneca Lake than in either of the other Finger Lakes. In the 

 former the maximum number of Cyclops was 25,100 per cubic meter in the o to 5 m. 

 stratum, with an average number of 21,460 in the upper 15 m. The maximum number 

 of Diaptomus was 9,810 per cubic meter in the 15 to 20 m. stratum of Seneca Lake. 

 Limnocalanus was present in the catches from each of the three Finger Lakes, but was 

 confined to the deeper water. 

 75412°— 22 16 



