534 TEN YEAES IN SWEDEN. 



These facts are quoted only to prove how difficult it is to 

 distinguish this and S. ferox from each other. In the 

 trout state, as Widigren properly observes, it is impossible 

 to distinguish S. tmtta and S. fefox from examples of S. 

 fario of the same size ; and it is often almost impossible to 

 distinguish individuals of the different forms of the same 

 size from each other, unless we know from what waters they 

 were taken. How, then, can we consider them as distinct 

 species ? Even in the common trout (S. fario, L.), Siebold 

 has detected many barren individuals. Without doubt such 

 may also be found in the north. 



It will be seen by the above description that in Scandi- 

 navia we have, as I consider, at present three species of 

 migratory salmon, and three species confined to the fresh 

 waters ; for I can hardly agree with Malmgren, and consider 

 the S. eriox, or bull trout, and the S. fario, L., common 

 trout, as nothing more than varieties of the S. trutta, L., or 

 salmon trout. I think there is much in his remarks respect- 

 ing the identity of our large lake trouts with the sea salmon 

 and the bull trout, and very probably these two fish are not 

 distinct species, but only degenerated forms of the sea fish, 

 changed by a long residence in fresh water. However, in 

 the present state of uncertainty (for after all it is only a 

 supposition that these two large lake trout are nothing more 

 than forms of the salt water species),! have deemed it best 

 to consider our two lake trout or salmon as distinct species, 

 and I think we may fairly erase from the list Mlsson's S. 

 ocla and 8. truttula. 



A careful study of sterility in members of this family will 

 probably lead to important results, and may account for many 

 a curious form of salmon or trout which has hitherto puzzled 

 our icthyologists. 



Eespecting the propagation of hybrids between the dif- 

 erent species of this genus, such as between the sea salmon 

 and common trout, I consider it a subject to be approached 

 with great caution. Without at all denying that a hybrid 

 fish can be produced as well as a hybrid bird, it seems so 

 contrary to all natural laws that I can never believe, except 



