Biological Survey — Oswego Watershed 169 



grounds before any of the eggs have been laid. The abdomen is 

 freely opened for its whole extent and the ovary — there is but one — 

 carefully dissected out. It is weighed entire on accurate 

 scales. Then, using chemical scales if possible, enough of the 

 ovary is cut away to weigh one gram. The eggs in this weight are 

 actually counted. Assuming that the number in a gram of ovary 

 is uniform throughout, the whole number present can be deter- 

 mined by multiplying the number in one gram by the number of 

 grams in the whole ovary. 



In case the eggs are not easily separated from the ovarian tissue, 

 the weighed gram can be macerated over night, or if necessary 

 longer, in 20 per cent nitric acid in water. After the nitric acid, 

 the piece of ovary should be soaked for half an hour or more in 

 water. Then the eggs are easily separated and counted. 



The following were the actual counts made for the different 

 lampreys and the number of eggs estimated in each : 



Sea lamprey from Lawrence, Mass., on the way to the spawning 

 grounds. 



Weight of the entire animal 640 grams 



Weight of the entire ovary 121 grams 



Number of eggs in one gram 1,950 



Number of eggs in the whole ovary of 121 grams. . 235,950 



Lake lamprey from Cayuga lake, before the spawning time : 



Weight of the entire animal 124.6 grams 



Weight of the entire ovary 45. grams 



Number of eggs found in one gram 2,406 



Number of eggs in the entire 45 grams 108,270 



Two other lake lampreys taken from the spawning beds yielded : 

 one, 63,000, the other 65,000. Evidently a part of the eggs had 

 already been laid. 



Brook lamprey (transforming) : 



Weight of the entire animal 8.5 grams 



Weight of the entire ovary. . 150 milligrams 



Eggs counted in 50 milligrams 1,092 



Entire number of eggs in the animal 3,276 



The transforming brook lamprey was used because it is prac- 

 tically impossible to secure a female at the spawning time which 

 has not already laid a part of the eggs. Dean and Sumner esti- 

 mated from a gravid female taken at the spawning time that she 

 contained 860 eggs. It seems almost certain that a part of the 

 eggs had been laid as with the lake lampreys from the spawning 

 grounds. (See above.) 



Death of Lampreys After Spawning. — The question is often 

 asked: What becomes of the lampreys after the eggs are laid? 

 The answer is simple and certain. They all die, and none of them 

 ever return to the ocean or the lakes to recuperate and prepare 

 for an additional generation. This has been the belief of fisher- 

 men for many years, also, of scientific men, for the ovaries aftei 



