BIOLOGY. 319 



NATURAL HYBRIDS. 



Dr. Fritz Miiller has recently directed Mr. Darwin's attention to 

 the barnacles occurring; on the coast of South America, and amon^ 

 others describes a natural hybrid between Balanus armatus and B. 

 assimilis, which he accounts for by tlie isolation of the respective 

 parents. If, he says, we regard the species of a genus as descend- 

 ants of a common primitive form, and, at the same time, in ac- 

 cordance with the well-known experience of gardeners, regard 

 their various peculiarities as so much better fixed, or so much less 

 variable, the earlier they were acquired, the longer they have 

 been inherited unchanged, it becomes intelligible that, above all, 

 the characters proper to the primitive form persist ; and consequent- 

 ly, in the crossing of two species, these are more readily trans- 

 ferred to the h3'brid than later acquired peculiarities of the parents. 

 He thus thinks to explain many peculiarities of hybrids, and per- 

 haps in many cases to trace from the form of the hybrids to the 

 primitive form of the genus ; the latter, of course, only with the 

 greatest care, for the mere fact that the hybrids produced by males 

 of one species with females of another do not agree with those 

 produced by males of the second species with females of the first, 

 furnishes a proof that other circumstances aid in determining 

 the form of the hybrids. — Quarterly Journal of Science, October, 

 1868. 



THE ARABIAN HORSE A SPECIFIC TYPE. 



M. Sanson, " Comptes Rendus," March, 30, 1868, in studying 

 the specimens in the museum of Paris, noticed several skeletons 

 of horses labelled " Arabian" which had only 5 lumbar vertebrae, 

 instead of 6, the normal number in the horses of Western Europe. 

 Examining also the collections of Germany, and from 14 authen- 

 tic specimens, he has arrived at the following conclusions: 1. 

 There exist in the Eastern countries two specific types of race of 

 the genus Equus, hitherto confounded under the name of the Ara- 

 bian or Oriental horse. 2. Both are brachycephalous, but in one 

 the forehead is flat, the nasal bones rectilinear, and the lumbar 

 vertebrae 6 ; in the other the forehead is convex, the nasal 

 bones slightly curvilinear, and the lumbar vertebrae only 5 ; 

 these vertebrae difi'er, not only in their number, but in the form of 

 their transverse processes, and their disposition in the series. 3. 

 These two types seem to have distinct geographical origins, as 

 they are evidently the issue of difi"erent stocks ; the type with 6 

 lumbar vertebrae would undoubtedly belong to the Asiatic conti- 

 nent; the type with 5 lumbar vertebrae to the African continent, 

 as the other African types of the genus, as the ass and the zebras, 

 acknowledged to be distinct species, have the same number, 4. 

 The reality of the specific type of this horse with 5 lumbar ver- 

 tebrae would explain many anomalies of the spine in the crosses 

 with this type, the evident result of a conflict of physiological 

 heredity. 



