i6 

 Cross Between Salmo fario and Salvelinus alpinus. 



The finest and largest series of hybrid trout which we have 

 seen is in the United States National Museum. It is the re- 

 sult of crosses between the saibling and brook trout of Nor- 

 way, artificially produced at one of the Norwegian fish cul- 

 tural stations, some years prior to the International Exposi- 

 tion at Philadelphia in 1876. These hybrids were exhibited 

 in the Norwegian section at the Centennial Exhibition, and 

 at the close of the Exhibition, were presented to the United 

 States National Museum. The collection contains individuals 

 ranging in age from one year to six years, and includes the re 

 suits of crossing both ways between the two species. 



In no instance does the hybrid resemble either parent in 

 general appearance. In shape there is a compromise between 

 the two parent forms. The saibling {Salvelinus alpimts) has 

 a forked tail, while the Salmo fario has the tail nearly truncate 

 when expanded. In the hybrid, until five years old at least, 

 individuals all have the tail more forked than in the brook 

 trout {fario) and less so than in the saibling. One of the 

 largest six-year-olds has the tail-fin truncate, about as it is in 

 salmo fn io. 



The proportions of the hybrid have already been hinted at 

 above. The height of the body equals more than the height 

 of the head, and is contained four and two-thirds times in the 

 length of the fish measured to the end of the scales. The 

 head is one-fourth of this same length and contains the dia- 

 meter of the eye about six times. The snout is half again as 

 long as the eye and one-half as long as the upper jaw. The 

 maxilla extends far behind the eye, the length of the upper 

 jaw being somewhat more than one-half the length of the 

 head. 



The teeth in the vomer are invariably similar to those of 

 the Salmo fario. In all but six individuals of this large series, 

 teeth are present and well developed on the base of the 



