114 
THE CALIFORNIAN SALMON. 
three other imported species it has only eleven to twelve. 
The dorsal fin has thirteen rays. The vertebrae are sixty- 
six in number, and the pyloric caeca one hundred and 
fifty-five. 
Amid the confused and doubtful distinctions, which it 
has been attempted to found, between the different species 
of the salmonidae, it is hard to find the way, which is 
rendered yet more difficult, by the many hybrids between 
the species which are believed to again cross with the pure 
forms, thus connecting one species with another by almost 
insensible gradations. The power of adaptation to circum- 
stances being strong in the genus, many apparently new 
species, have probably been formed by accidental hybrida- 
tion in the first instance, and the new form has been fixed 
by breeding to the same type over a long period, the new 
race, from being exposed to somewhat altered conditions, 
becoming apparently a distinct species. 
In a preface to the sixth volume of the Catalogue to the 
fishes in the British Museum, Dr. G-unther remarks : — “The 
salmonidae and the vast literature on this family offer so 
many and so great difficulties to the icthyologist, that as 
much patience and time are required for the investigation 
of a single species, as in other fishes for that of a whole 
family. The ordinary method followed by naturalists in 
distinguishing and determining species is here utterly 
inadequate ; and I do not hesitate to assert that no one, 
however experienced in the study of other families of 
fishes, will be able to find his way through this labyrinth 
of variations without long preliminary study, and without 
a good collection for constant comparison. Sometimes 
forms are met with so peculiarly and so constantly 
characterised, that no icthyologist who has seen them will 
deny their specific rank ; but in numerous other cases, one 
is much tempted to ask whether we have not to deal with 
