170 Conservation Department 



spawning- contain no immature eggs as with animals that lay 

 eggs more than one season. For the sea and the lake lampreys 

 the number of dead ones found in the streams shows at least 

 a high mortality. Mr. Holmes of Lawrence, Mass., who has col- 

 lected sea lampreys for many years as they went up the fish- 

 ways, wrote to me that he had seen all kinds of fish going up 

 and down, but he never saw any large lampreys on their return 

 to the ocean. He often found the small, just transformed ones 

 going down, but never the large ones. Much evidence also came 

 from fishermen familiar with the sea lamprey that they all die after 

 spawning. 



Proof that the Lampreys Die After Spawning. — Brook 

 lampreys have been kept under observation after spawning, and 

 they always die in a relatively short time. There are no micro- 

 scopic eggs in their spent ovary, and as these animals never feed 

 after transformation, even before spawning, it is certain that they 

 die soon afterward. Dead ones have also been found in the spawn- 

 ing streams, and sometimes these dead ones are so covered with 

 the mold, Saproiegnia, that they look as if wrapped in cotton. 

 That the lake lampreys die after spawning seems probable from 

 the anatomical degeneration of the liver and intestine, and from 

 the absence of minute ova in the ovary. Also from the number 

 of dead animals found in the spawning stream. 



Experimental evidence. — As the situation in Ithaca is so favor- 

 able it seemed that the opportunity to make a crucial test should 

 not be neglected. Some vigorous lake lampreys from the spawning 

 beds were put in a covered spring with bullheads to see if they 

 would feed upon them. As will be shown later, the lampreys 

 during their predatory life attack fish in an aquarium as readily 

 apparently as in the waters of the lake, therefore it seemed that 

 this was a fair trial. The water of the spring was cold. All of 

 the lampreys died, although the bullheads (Ameiurus) lived for a 

 long time. To make the experiment as normal as possible a wire 

 cage was placed in the spawning stream in deep water, and bull- 

 heads and lamprfeys put into it. As before the fish lived, but the 

 lampreys all died. As the assumption always is that the lampreys 

 return to the lake before they commence to feed, another cage 

 was sunk in the lake and lampreys and bullheads added. The 

 bullheads were used because the lampreys are particularly fond 

 of bullheads and the experiment attempted to make the conditions 

 as favorable as possible. The lampreys died as before, but the 

 bullheads did not. 



Persistence of the Notochord. — It is often argued that if the 

 lampreys all died after spawning their dead bodies would be more 

 in evidence. This season (1927) and the season of 1911 were 

 especially favorable for testing the matter. It is evident that 

 if there were heavy rains and consequent high water, the dead 

 bodies would be washed down stream and quickly disappear, but 

 on the dates mentioned there was very little rain and the streams 



