68 SALMONIDiE. 



water iu warm rooms, the eggs were matured almost imme- 

 diately, and the young fry hatched. In this state they can 

 be preserved in the bottles, with the water unchanged, for 

 about ten days, as during that time they are supported on 

 the yolk of the egg which adheres to the under part of their 

 bodies, as exhibited in figure 1 on the cut at the head of 

 this article. 



On the 23rd of March, according to Dr. Knox, the ova began 

 to change, and it was not until the 1st of April that the fry 

 were found to have quitted the beds. 



Mr. Shaw's experiments were, however, so conducted as to 

 furnish data on which more reliance may be placed ; and as 

 these are of the greatest interest, and as from experiments 

 similarly conducted, farther results of a different kind might be 

 attained, of surpassing importance, I shall state them somewhat 

 at length. 



A full account will be found, by those who desire to investi- 

 gate the subject more thoroughly, in the Edinburgh New 

 Philosophical Journal for July, 1836, and January, 1838. 



Mr. Shaw, it seems, caused three ponds to be made, of dif- 

 ferent size, at about fifty yards distance from a Salmon river, 

 the Erith, the ponds being supplied by a stream of spring- water, 

 well furnished with the larvse of insects. The average tempera- 

 ture of the water in the rivulet was rather higher and less 

 variable than of that in the river ; otherwise the circumstances 

 of the ova contained in the ponds, and of the young fry pro- 

 duced therefrom, were precisely similar to those of the spawn 

 and fry in the river. 



These ponds were all two feet deep, with well-gravelled 



