734 THE AMEBIC AN NATURALIST [Vol. XLVI 



had been for some time by herself on an adjoining nest. 

 During the time the three "fish" were on the one nest 

 (Figs. 2 and 5) they all took part in repairing it, in 

 the intervals between mating — the male apparently not 

 distinguishing between the female of his own nest and 

 the intruder. In two other cases there was one indi- 

 vidual to a nest. After carrying a stone out the lamprey 

 immediately returns for another. This is repeated a 

 number of times and then the lamprey clings to a stone 

 apparently exhausted (Fig. 4). Now and then the tail is 

 Hashed against the sides of the nest to pad it down. When 

 on a nest by itself, a lamprey occasionally wanders a 

 distance of some feet— even several hundred feet— but 

 invariably returns to continue its nest-building. These 

 wanderings are perhaps for the purpose of finding a 

 mate. 



Mating.— The method of copulation is similar to that 

 of the brook lamprey, Lampetra ivilderi, as described by 

 Dean and Summer ('97); and it is unnecessary to re- 

 describe it here. I will merely comment on a few de- 

 tails. The female must cling to a large stone in the 

 nest in order that copulation take place. The male 

 seizes her by the top of the head. In copulo, the two are 

 arranged so as to form an ellipse. The caudal portion 

 of the male is applied immediately back of the first dor- 

 sal of the female, and curved in a loop around her body. 

 Severn ) authors have referred, in the case of both Amer- 

 ican and European lampreys, to the vibration of the 

 posterior portions of the "fish," in copulo. In the sea 

 lamprey this vibration may be observed very closely. It 

 lasts two or three seconds. It begins slowly, gradually 

 increases in frequency until it reaches an exceeding ra- 

 pidity of vibration, then subsides by a few slow beats. 

 The motion strongly suggests the vibration of a rattle- 

 snake's tail in the warning pose. Indeed while watching 

 the lampreys one can hardly keep from imagining the 

 sound which ought to accompany the lampreys' vibra- 



