498 The Cyclostomes, or Lampreys 



it is ready to be used as a spawning bed or nest. A great many 

 nests are commenced and deserted. This has been left as a 

 mystery in publications on the subject, but Ave are well con- 

 Adnced that it is because the lampreys do not find the' requi- 

 sites or proper conditions of bottom (rocks, sand, etc., as given 

 below) to supply all their needs and fulfill all conditions for 

 ideal sites. This desertion of half -constructed nests is just what 

 would be expected and anticipated in connection with the ex- 

 planation of 'Requisite Conditions for Spawning,' given below, 

 because some shallows contain more sand and fewer stones, and 

 others contain many larger stones but no sand, while others 

 contain pebbles lying over either rocks or sand. The lamprej^s 

 remove some of the material, and if they do not find all the 

 essentials for a spawning nest, the site is deserted and the 

 creatures move on. 



Requisite Conditions for Spawning with Lampreys. — "For a 

 spawning site two conditions are immediately essential — proper 

 conditions of water and suitable stream bed or bottom. Of 

 course with these it is essential that no impassable barriers 

 (dam or falls) exist between the lake and the spawning sites 

 to prevent migration at the proper 'running' season. Lampreys 

 wdl not spawn where there is no sand lying on the bottom 

 between the rocks, as sand is essential in covering the eggs 

 (see remarks on the ' Spawning Process ' ) ; neither will they 

 spawn where the bottom is all sand and small gravel, as they 

 cannot take hold of this material with their mouths to con- 

 struct nests or to hold themselves in the current, and they 

 would not find here pebbles and stones to carry over the nest 

 while spawning, as described elsewhere. It can thus be seen 

 that, as suggested above, the reason they do not spawn in 

 Fall Creek and Cascadilla Creek, between the lake and the 

 falls, is that the beds of these streams are very rocky, being 

 covered only with large stones and no sand. There is no doubt 

 that the lampreys find here suitable conditions of water, but 

 they do not remain to spawn on account of the absence of the 

 proper conditions of stream bed. Again, they do not spawn 

 in the lower course of the inlet for a distance of nearly two 

 miles from the lake, because near the lake the bed of the stream 

 is composed of silt, while for some distance above this (up- 



