590 
to establish the fact of the interbreeding of the two species, still 
point strongly in that direction. 
There seem to be in Nature several analogous cases in which 
two closely-allied species, not only often, but habitually, interbreed. 
This appears to be the case, among the Molluscs, with Helix 
nemoralis and H. horlensis ; among plants, with Primula vulgaris 
and P. veris ; and also, probably, in the genera Viola, Rosa, Rubus, 
Verhascum, &c. But perhaps the best-known instances occur 
among the birds. That of the interbreeding of the Carrion and 
Hooded Crows will at once suggest itself. This has been known 
to take place frequently in Scotland, and occasionally in England ; 
but in Russia and Siberia it appears to be carried out on almost 
astonishingly extensive scale. Mr. H. Seebohm has given a most 
interesting account of his observations upon the hybridization 
of these two species, in the ‘Ibis’ for 1878. It seems that 
the whole of Russia and W estern Siberia is one vast colony 
of Hooded Crows ; Eastern Siberia, on the other hand, is an 
equally vast colony of Carrion Crows. In the wide intermediate 
region, about one-fourth of the Crows are pure Hoodies, one- 
fourth pure Carrions, and the remaining half are hybrids of 
every description. Mr. Seebohm also says of the Grey Shrikes 
Lanius excubitor and L. major: “After my experience of the 
Crows, 1 should not be surprised to find that on the boundary 
line of their geographical distribution they occasionally, if not 
habitually, intermarry.” It seems also impossible to doubt, after 
what Professor S. E. Baird has said in his ‘ Report on the Pacific 
Railroad Survey,’ that the various members of the genus Garpodacus 
habitually interbreed ; while two members of the genus ColapAes 
((7. auratus and G. mexicanus) appear to afibrd an instance very 
similar to that of the Crows. The former abound in all the 
Eastern States; the latter in all the Western; and the two run 
into one another in the central region through a most extraordinary 
variety of hybrids. Doubtless other instances would not be hard 
to find. 
Note.— I ll consequence of Mr. Christy’s absence from England, the 
above paper has not been revised by him. [Bn.] 
