The Lake and Brook Lampreys of New York 431 



DeKay's name was based, prove to be the larvse of the marine 

 lamprey, which is probable (see Jordan and Fordice, '85, p. 

 284). 



Distribution of the Lake Lamprey. — It is known by personal 

 observation and collecting, to be abundantly present in Cayuga 

 and in Seneca Lakes ; and from information obtained concern- 

 ing the other lakes and from L,ake Ontario, it is believed to be 

 present in them also. It is hoped that during the next five years 

 all of these regions can be visited and all the lakes and water- 

 courses of the State investigated to determine the presence of 

 lampreys and their correlation with those now under consider- 

 ation. It is hoped also to extend the investigation to the 

 Great Lakes and to bring any lampreys there living into the 

 field of comparative observation. 



Comparison of the Sexes. — As stated above, except in the 

 spawning season there are no definite external characters by 

 which the se.-ces can be distinguished. The question then 

 arises as to the necessary steps to make the determination, at 

 any other time than in the spawning season. The only way, 

 so far as is known to the writer, is to resort to dissection. 

 This is the only way also for determining the sex in the lar- 

 vae. Upon dissection, even in larvae loomilimeters in length, 

 the sexes may be quite readily distinguished by examining 

 the gonads, as the ovary and the ova are markedly larger than 

 the spermary and sperm mother-cells (PI. VII, fig. 37, 38). 

 The determination of the sexes in large, adult forms is much 

 more difficult. The ovary and spermary are alike single foli- 

 ated or lobulated organs, and the sperm mother-cells project 

 from the surface of the spermary as do the ova from the ovary, 

 so that from the gross appearance alone, it is not easy to dis- 

 tinguish the two generative glands. When examined as 

 opaque objects, with a lens or with a compound microscope the 

 same difficulty is experienced, but if treated by any of the 

 approved histological methods the true nature of the elements 

 in each case unmistakably appears (PI. VII, fig. 27 A, 29 A 

 and 28, 30). 



After one has become accustomed to distinguish the sexes 

 by dissection, the differences observable by the eye or with a 



