196 Marsh — Limnetic Crustacea of Green Lake. 



epischura lacustris — continued. 



No. 



Total. 



No. 



Per cent. 



of Coll. 



0-5 



5-10 



10-15 



15-20 



20-25 



25-30 



30-35 



35-40 



40- 



10.96.. 



140 



131 



54 



30 



29 



203 



397 



333 



270 



107 



100 



120 



1 46 



150 



46 



98 



9 



4 



61.43 



61.07 



44.44 



53.33 



27.59 



99.01 



84.63 



76.58 



91.48 



61.68 



28. 



46.66 



34.79 



69.33 



69.56 



93.88 



in0.20 



100. 



34.29 

 7.63 

 44.45 

 13.33 

 48.28 

 .99 

 11.34 

 21.32 



37.38 



72. 



40. 



34.78 



21.34 



15.22 



1.43 

 30.54 

 11.11 

 33.34 

 20.68 



.71 

 .76 







.71 





1.43 



11.96.. 









12.96.. 













13.96.. 















14.96.. 



3.45 













15.96.. 













16.96.. 



4.03 

 1.80 

 5.93 















17.96.. 



.30 



2.22 



.94 













18.96.. 





.37 









19.26.. 









20.96.. 













21.96.. 



13.34 



26.09 



5.34 



15.22 















22.96.. 



2.17 

 2.67 



2.17 











23.96.. 





.66 



.66 





24 96.. 









25.96.. 



3.06 



1.02 



2.04 









26.96 . 



met'rs 











27.96.. 



































From the table it appears that Epischura occurs in the sum- 

 mer and fall months, with no very well defined time of maxi- 

 mum numbers. (See PI. VIII.) The largest numbers obtained 

 at single hauls were 390 in the evening of October 9, 1894, 

 395 from a haul made through the ice on March 9, 1895, and 

 397 on August 24, 1896. In the March haul a large proportion 

 were larval forms. Epischura disappears entirely in the latter 

 part of March and does not appear again until June. 



The number of my winter collections was, unfortunately, very 

 small, so that one must be very careful about drawing infer- 

 ences from them. But I think we may consider it fairly cer- 

 tain that Epischura is hatched from the egg in the winter, — 

 probably in February or the early part of March. This in itself 

 is a matter of some interest, as, so far as I know, there is no 

 previous record of the occurrence of any considerable number 

 of larval forms of Epischura. 



It is a curious fact that so soon after the appearance of the 

 larval forms, Epischura entirely disappears for several months. 

 I will not in this paper hazard a conjecture as to the explana- 



