208 Marsh — Limnetic Crustacea of Green Lake. 



With the exception of three individuals in the collection of 

 March 27, 1895, I found no Leptodora from the latter part of 

 October to the middle of June. It was present pretty generally 

 in the summer collections, but never in very large numbers. 

 The largest number that I obtained in any collection was 

 twenty-four. 



In its vertical distribution, Leptodora is commonly within ten 

 meters of the surface. I have found individuals at a depth of 

 between twenty-five and thirty meters, but it is not a common 

 occurrence. 



Leptodora was never present in sufficient numbers in my col- 

 lections so that I could draw any inferences in regard to the 

 effect changes of temperature would have on its vertical distri- 

 bution. 



It will be noticed that my observations in regard to the sea- 

 sonal distribution of Leptodora correspond very closely with 

 what Zacharias says of Leptodora in Ploener See, for he states 

 that it disappears in the course of the month of October, and 

 appears again towards the end of May. (Zacharias, '94, p. 100. 

 Also, Apstein '96, p. 175. Fric and Vavra, '94, pp. 55, 108.) 



Apstein ('96, p. 80) states that Leptodora is found most abun- 

 dantly in the deep water. This is certainly not according to my 

 observations, as they would indicate that it should rather be 

 considered a surface form, although it is by no means confined 

 to the immediate surface. As Apstein does not state what he 

 means by deep water in this case, the seeming contradiction in 

 our observations may be more apparent than real. 



