The Zoologist — November, 1874. 4205 



ITotitfs flf ieto §ooIis. 



The Birds of Shetland, with Observations on their Habits, 

 Migration and Occasional Appearance. By the late Henry 

 L. Saxby, M.D., of Balta Sound, Unst. Edited by his 

 Brother, Stephen H. Saxby, M.A., Vicar of East Clevedon, 

 Somerset. Deniy 8vo, 398 pp. letterpress, eight tinted litho. 

 plates. Edinburgh : Maclachlan and Stewart. London : 

 Sirapkin, Marshall and Co. 1874. 



(Secon-d Notice.) 



Dr. Saxby, in writing of the eggs of the hooded crow, says, 

 " They are four in number, and, as a rule, precisely similar to 

 those of the carrion crow;" but I find no allusion to the possibility 

 of these two birds constituting a single but dimorphic species. 

 Mr. Hewitson has this passage under "carrion crow": "T have 

 chosen the figures of the plate that they might not only represent 

 each its own species, but that of the nearly allied species as well ;" 

 and under "hooded crow," he says, "The eggs are four or five in 

 number, and do not differ from those of the carrion crow or rook, 

 except in size." The question "What is a species?" I have 

 attempted to solve (S. S. 1345) in these words — "I conceive a species 

 to be composed of such living individuals as possess perfect 

 eugenisra among themselves ; that is of individuals any pair of 

 which can reproduce their kind, their descendants being equally 

 prolific ; and I conceive also that all structural characters, whether 

 of form, size, or colour, are insufficient to the differentiation of 

 species; not useless, but insufficient." So far as I know, this idea 

 has not made a single convert; but I cling to it still, hoping that 

 some day or other it may be received with more favour. My readers 

 will perceive how intimately it bears on the specific identity or 

 distinctness of the two crows. 



Temminck tells us that they breed together: he says — "The 

 black and hooded crow sometimes breed together; they produce 

 mongrels which resemble one or other of the species : this occurs 

 in the southern and eastern countries of Europe, where the black 

 crow is uncommon, but we find no instance of it where both species 

 are common." — Temminck, i.l09. Under " hooded crow" Temminck 



SECOND SERIES — VOL. IX. 3 F 



