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THE AMERICAN NATURALIST [Vol. XLVI 



greatly augmented through continual rubbing against 

 stones, padding down the nest, etc. 



Fate of Sea Lampreys After Spawning. — From the 

 facts at hand, it appears that lampreys that go up the 

 river to spawn do not again return to the sea, but die 

 shortly after spawning. I found two dead, badly 

 scarred, spent lampreys in the river not far from de- 

 serted nests. One was in the shade of tall grass near 

 the bank, the other tangled in weeds and twigs in the 

 middle of the river. Both had been rasped, apparently 

 for food, by other lampreys. Burroughs ('83), also re- 

 cords that it is not unusual to find dead lampreys in 

 June. 



The causes of the death of these lampreys— and in- 

 deed of all anadromous fishes — are still rather obscure. 

 Death is probably chiefly due to the cycle of katabolic 

 processes initiated on the maturing of the gonadial 

 products. Besides this at least two other causes must 

 be regarded as contributary : first the greatly lessened 

 vitality due to the constant exertion in uprooting and 

 transporting stones. Lampreys thus weakened become 

 the prey of other lampreys. Secondly, the numerous 

 scars or wounds which they inflict on one another in 

 mating allow ' 1 fungus" to invade, and ultimately to de- 

 stroy, their tissues. All three of these causes, probably, 

 play a part in causing the death of the sea lampreys after 

 spawning. 



Remarks on the Senses and Mentality of the Sea Lam- 

 prey. — The behavior of the lampreys was carefully noted 

 to see in how far their senses come into play in building 

 the nest and in other activities. The general impres- 

 sion was that the sea lamprey is guided by touch more 

 than by any other sense. Sound does not disturb them 

 while on the nest : one may carry on a conversation right 

 over a nest without in the least affecting them. Indeed 

 one lamprey that was building a nest under a wooden 

 bridge was not disturbed by the clattering of automo- 

 biles over it. This insensitiveness to sound may mean, 



