127 



DdpJniia rdrociina. — It was rnrely found at a gTeater depth thau 

 seven meters. liotli youn.i;' and adult were one to three meters below the 

 surface on clear days. Both appeared at the surface in the evening about 

 half an hour after sunset. In tiie morning-, however, the adults left the 

 surface before the young. The young usually disappeared about siuirise 

 wliile the adults moved down from tlie surface an hour or more before 

 sunrise. The surface maxinnun of young and adults combined, was found 

 three-quarters of an hour after sunset in the first all-night series and 

 lialf an liour later in the second, aliout S p. m. in eacli case. 



l)i(il)h(innsi)iii(i Jtrdclii/uniiii. — A (■(unitaratively small number of this 

 species was found. It was rather irregular in its movements but, in gen- 

 eral, it appeared at the surface thirty to forty-five minutes after sunset 

 and left the siu'face an hour or more liefore sunrise. It was found at a 

 dei)th of one meter, usually, in the da.\ time, and rarely occurred in catches 

 lielow a depth of seven meters. 



C'erioddphiiia hicustris. — This form was confined to the upper four 

 meters and was present in very small numlK'rs. Tliere was no diurnal 

 movement shown by it. 



Lt'ptodiim hyalina. — Only a small number were found. It occurred in 

 only Hve of the twenty day series. In tliese five instances, it was con- 

 iined to the region of the thermocline, that is, between four and eight 

 meters. Botli young and adult appeared at the surface in the evening 

 from tliirty to forty-five minutes after sunset. The young left the surface 

 al>ont an hour l)efore sunrise and the adults half an hour or more earlier. 



Chiidunis and Bosmiiia were found in very small numbers. No diurnal 

 movement was noted. 



r///>//.s-.— Tliere was. apparently, an extended horizontal migration of 

 Cypris as it was found in a third of the morning and evening series, and 

 these observations were made in tlie deepest part of the lalie. In the day- 

 time. lidwcNcr. Cypris was never found in the limnetic region of the lake 

 )>ut in file littoral region. 



A few Coirtlira larv;t> were found in and below tlie thermocline in the 

 daytime. In a few instances they came to the surface at niglit. 



Jx'oti [cm. -The rotifi-rs showed no diurnal movement. With respect 

 lo their vertical dlstriliuiion, they form three groups: 



1. Maxti(/()C('rrn, Pal ijarthm , and A-'<j)iaiir]iin( were confined to the upper 

 five, six and seven meters respectively, or the region in and above the 

 thernKtcline. 



