220 REPORT OF THE COMMISSIONERS OF 



Tl)e Spawning Process. 



There is much of interest in the study of the spawning process, as it is for the 

 maintenance of the race that the lampreys risk and end their lives ; and as they are 

 by far the lowest forms of vertebrates found within the United States, a consideration 

 of their actions and apparent evidences of instinct becomes of unusual attraction. Let 

 us consider one of those numerous examples in which the male migrates before the 

 female. When he comes to that portion of the stream where the conditions named 

 above are favorable, he commences to form a nest by moving and clearing stones, and 

 making a basin with a sandy bottom about the size of a common washbowl. Several 

 nests may be started and deserted before perfect conditions are found for the 

 completion of one. The male may be joined by a female either before or after the 

 nest is completed. There is at once harmony in the family ; but if another male 

 should attempt to intrude, either before or after the coming of the female, he is likely 

 to be summarily dealt with and dismissed at once by the first tenant. As soon as the 

 female arrives she, too, commences to move pebbles and stones with her mouth. 



Sometimes the nest is made large enough to contain several pairs, or often unequal 

 numbers of males and females ; or they may be constructed so closely together as to 

 form one continuous ditch across the stream, just above the shallows. Many stones 

 are left at the sides and especially at the upper margin of the nest, and to these both 

 lampreys often cling for a few minutes as though to rest. While the female is thus 

 quiet, the male seizes her with his mouth at the back of her head, clinging as to a fish. 

 He presses his body as tightly as possible against her side, and loops his tail over her 

 near the vent and down against the opposite side of her body so tightly that the sand, 

 accidentally coming between them, often wears the skin entirely off of either or both 

 at the place of closest contact. (This is plainly illustrated at the side of the tail 

 of the male Lake Lamprey, shown as No. la in this article. For an illustration of the 

 positions of the sexes at the instant of spawning, see the picture of the pair in the 

 upper right corner of "Brook Lampreys on Spawning Nest.") In most observed 

 instances the male pressed against the right side of the female, although there is no 

 unvarying rule as to position. The pressure of the male thus aids to force the eggs 

 from the body of the female, which flow very easily when ripe. The vents of the two 

 lampreys are thus brought into close proximity, and the conspicuous genital papilla of 

 the male (plainly shown in the illustration) serves to guide the milt directly to the 

 issuing spawn. There appears to be no true intromission, although definite observa- 

 tion of this feature is quite difficult and, in fact, impossible. During the time of 

 actual pairing, which lasts but a few seconds, both members of the pair exhibit 

 tremendous excitement, shaking their bodies in rapid vibrations, and stirring up such 



