Marsh — Limnetic Crustacea of Green Lake. 



215 



daphnella — 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- 



15.96.. 



201 



141 



143 



65 



211 



88 



22 



12 



12 



2 



99.50 

 56.74 



2.80 

 73.85 

 15.16 

 54.55 

 18.18 

 66.67 



8.34 











.50 



2.12 



.70 









16.96.. 



31.21 

 5.59 

 24.61 

 51.87 

 36.36 

 45.45 

 8.33 

 16.67 



8.5± 

 89.51 



'26.54 

 9.09 



36.37 



25. 

 8.34 



50. 







1.42 







17.96.. 



1.40 

 '".'95 



i.54 







18.96.. 









19.96.. 



.48 









20.96.. 









21.96.. 















22.96.. 















23.96.. 



66.65 

 50. 













24.96.. 













25.96.. 

















26.96.. 























27.96.. 





































, 









Daphnella is at its maximum in point of numbers from about 

 the middle of August to the middle of September. From the 

 last of October to the last of June, very few are found. Only 

 in one collection made during the winter months did I find any 

 Daphnella, — that of March 27, 1895. Fric and Vavra ('94 r 

 p. 103) state that Daphnella occurs from April to October. The 

 observations of Apstein ('96, p. 166) very nearly agree with 

 mine. 



In regard to its vertical distribution, Daphnella may be found 

 at any depth. By far the larger number, however, occur in the 

 upper layers, ordinarily from seventy to eighty per cent, being 

 found within ten or fifteen meters of the surface. 



In order to get at the facts in regard to its vertical distribu- 

 tion, and possible migrations, I computed the average percent- 

 ages in the upper four or five levels for the day and night col- 

 lections of October, 1894, for the August collections, — all taken 

 in the daytime, — of 1896, for the September and October col- 

 lections of 1894, and for the collections of 1893, about twenty 

 in number, made within two or three days in the latter part of 

 August, with the following results: 



