À STUDY ON TROUT AND YOUNG SALMON. 243 



23 cm. 21,5 cm. 



2ö,o „ 26 „ 



25 „ 31,5 



22 „ 30 



27 „ 28.5 



The largest one weighed kgr. 0,60. 



During their growht in the aquarium a large proportion of 

 these fishes have suffered larger or smaller læsions to the fins 

 of the hindpart of the body. In some the ventrals and the 

 anal fin are a little worn as a consequence of the ravages of 

 the saprolegnia previous to their transfer to salt water. In some 

 the caudal fin is more or less hurt. Not a few have regenerated 

 the fins affeced. 



During the whole of their developement these^ young salmon 

 have been higly differing from any trout I have ever cought. 

 They distinguish themselves not only by peculiarities in the 

 structure and relations of several important parts of the body, 

 besides also in the colouring from all those fishes which I have 

 cought during my experiments and named trout. 



Their whole deportment and their habit in the aquaria also 

 shows a specially marked difference from those of the trout 

 which I have captured and kept in confinement for compa- 

 rison. 



All the trout, which I have kept in captivety, will keep 

 very still in the aquarium, suspended in midwater without hardly 

 any motion all day through, occasionally when gorged with food 

 resting motionless at the bottom. Off and on they will suddenly 

 dart forward catching their food when they are hungry. 



The salmon on the contrary are constantly in motion, nearly 

 unseasingly swimming round and round in the aquarium night 



