442 Simon Hoiry Gage 



orable one ma}^ see five to ten nests within a small radius ; 

 and perhaps the explanation of the very large nests may be 

 that several pairs commenced to build in such close proximity 

 that before they had finished, the nests run together thus pro- 

 ducing a single large nest with two or more pairs. Whenever 

 the nest is especially large it has an appearance of a' rounded 

 ditch, across the stream not parallel with it. 



If one observes the nest building throughout the season it 

 will be seen that those found earliest and those farthest up the 

 stream, contain but one lamprey, and usually the single one 

 is a male. It would thus appear that away down in the very 

 stem form of the vertebrate series the male is the house-builder 

 and takes the lead in preparing for the offspring. The female 

 is not by any means a sluggard, however, and when she joins 

 the male, sets to work with all her might to help complete the 

 nest. 



As stated above, the place most commonly selected for a 

 nest is in moderately swift water just above ripples. Now to 

 build the nest the animal has neither hands nor feet, only a 

 mouth, but the mouth is perfectly adapted for grasping by 

 suction and so the lamprey heads up stream, fastens to a stone, 

 the stone being frequently more than twice as heavy as the 

 animal itself. Then with powerful backward or side wise 

 swimming movements the stone is loosened and dragged down 

 the stream a distance a little greater than the length of the 

 animal, here it is deposited and another grasped and carried 

 down, and so on. If the stone is small it may be carried down 

 by being lifted free from the bottom (PI. VII, fig. 39). Some- 

 times a stone will not yield to the most vigorous tugs. In 

 such a case it would be very pleasant to say that two or more 

 joined forces. Two may attach to the same stone if it is large 

 but two have never been seen by the writer to actually join in 

 moving a stone. On the other hand the smaller stones are 

 removed from around the larger one, and from time to time 

 the efforts to remove the large one are renewed until finally it 

 yields to the combined force of the lamprey and the current. 



The nests are usually somewhat oval and the diameter 

 parallel with the stream somewhat greater than the length of 



