44^ Simon Henry Gage 



might have actually died, however, for birds of prey hovering 

 over the water would be very liable to catch any that were in 

 extremis. Nature has so many ways to dispose of dead bodies 

 that the number seen even on careful investigation is small, 

 even though the actual mortality may be great. 



In the last part of the season mau}^ were affected by sapro- 

 legnia, especially where the epithelium had been injured by 

 the attachment of another lamprey. An additional argument 

 in favor of tlie death of the lampreys after spawning, is the 

 condition of the alimentary canal and the liver. There would 

 need to be almost a new building of the alimentary canal. 

 And then enforcing the argument from the absence of small 

 ova in the ovary after spawning it is to be said that even in 

 the larva the eggs are of considerable size (PI. VII, fig. 38), 

 so that if the lampreys that had spawned were to return to the 

 lake and re-acquire ova a greater development in the ovary 

 would be required than takes place between late larval life 

 and sexual maturity ; a development requiring from two and 

 one-half to three and one-half years in the lake lamprey. 



An effort was made to determine the matter experimentally 

 by transferring lampreys that had spawned to water contain- 

 ing cat-fish {Aniiicrus nebulosus), as the lampreys seem partic- 

 ularly fond of cat-fish. The conditions were very unnatural 

 as the only available place was a cold spring. The cat-fish 

 soon died and the lampreys also, without attempting to feed 

 on the live or dead fish. It seems to the writer that the 

 experimental method is the only one promising satisfactorily 

 to settle this vexed question, a question important alike from 

 the scientific and from the economic stand-points. If a pond 

 through which the water from the stream in which they spawn 

 or one connected with the lake were stocked with cat fish or 

 suckers {Avmirus or Caiosto77i7is), fishes which are frequently 

 attacked by lampreys, and then if lampreys were placed there 

 after spawning one could determine the duration of life after 

 spawning under natural conditions of water and plentiful food. 

 There is no difficulty whatsoever in keeping lampreys alive 

 and in good condition out of the spawning season even in a 

 large aquarium where there are other fishes. Indeed the lam- 



