Biological Survey — Oswego Watershed 167 



stones the lamprey attaches its sucking disc to the stone and then 

 by powerful swimming jerks pulls the stone loose. If the stone 

 is small it is lifted up and carried down the stream (Fig. 1, No. 7). 

 If the stone is too large to lift the lamprey drags it along down- 

 stream to the edge of the nest. By working more in the middle 

 than around the edges the nest is deeper and freer from stones 

 in the middle and assumes the wash-bowl shape. This also leaves 

 sand and fine gravel in the middle. 



Most often there are but two to a nest, but sometimes there 

 may be five or six of the lake lampreys and sometimes as many 

 as twenty of the brook lampreys. All may be working to build 

 and perfect the nest. I have watched them by the hour but have 

 never seen two lampreys pulling the same stone although one in- 

 dividual often needed help badly. Others, however, have described 

 such joint efforts. Occasionally there is a stupid lamprey which 

 after carrying a stone to the edge brings it back and drops it in 

 the middle. Mostly, however, they act as if they knew exactly 

 what to do and proceeded to do it. 



Egg-Laying : When the nest is partly finished the egg-laying 

 may begin if the female knows that some of the eggs are ready. 

 The ovary is a single, elongated body extending practically the 

 whole length of the abdominal cavity and filling it almost com- 

 pletely. The eggs at the caudal or hinder end ripen first and are 

 shed into the abdomen. There is a short tube extending from 

 the abdominal cavity to the exterior (the genito-urinary tube). 

 The eggs and milt which are shed into the abdomen are forced out 

 through this tube into the water. 



When the female is ready to lay a batch of eggs she fastens 

 her mouth to a large stone at the side of the nest, and the male 

 fastens his mouth to the back of her head and twists his body 

 partly around hers (Fig. 3). Then, both arch their backs some 

 what to bring their tails down to the sand and fine gravel in the 

 middle of the nest. They both vibrate their tails with great 

 rapidity, "shake-together" as it is called, and stir up the sand 

 and gravel into a kind of cloud. At the same time the muscles 

 of the abdomen contract powerfully and force the eggs and milt 

 out through the abdominal pore into the mixture of water and 

 gravel. If the operation takes place in a good light, especially 

 if the sun is shining on the nest, one can see the stream of white 

 eggs pouring out into the cloud of sand and gravel. If the nest 

 is examined immediately after an egg-laying many eggs will be 

 seen scattered over the bottom of the nest, and if one takes up 

 some of the sand it will be found that the eggs are sticking to the 

 bits of sand and gravel. 



Before the eggs are laid the ovary puts on each one a coating 

 which becomes very sticky. just as soon as it gets into the water. 

 This enables the eggs to stick to the sand and gravel which the 

 lampreys stir up when they shake together. The heavy sand par- 

 ticles sink quickly and carry the eggs down into the nest instead 

 of letting them float downstream. 



