344 Miscellaneous. 



tures on Histology, vol. i. fig. 41, 8vo, Lond. 1852), as he remarked 

 to me when we examined them under a magnifying power of about 

 350 diameters ; but the canaliculi of the corpuscles are not quite so 

 distinct in the Arbutus as in the Pear. 



As to their chemical composition, Dr. Davy kindly examined them 

 at my request, and reports that " they consist chiefly of vegetable 

 matter, and contain only a very small proportion of lime, with a trace 

 of phosphate of lime." ' 



Abstract of a Lecture by Prof. T. H. HUXLEY, F.R.S., on Species 

 and Races, and their Origin, delivered before the Members of the 

 Royal Institution, on the Evening of Friday, February 10, 1860. 



THE speaker opened his discourse by stating that its object was to 

 place the fundamental propositions of Mr. Darwin's work 'On the 

 Origin of Species by Natural Selection ' in a clear light, and to con- 

 sider whether, as the question at present stands, the evidence adduced 

 in their favour is, or is not, conclusive. 



After some preliminary remarks, in the course of which the speaker 

 expressed his obligations for the liberality with which Mr. Darwin 

 had allowed him to have access to a large portion of the MSS. of his 

 forthcoming work, the phenomena of species in general were con- 

 sidered the Horse being taken as an example of such species. The 

 distinctions between this and other closely allied species, such as the 

 Asses and Zebras, were considered, and they were shown to be of 

 two kinds, structural or morphological, and functional or physio- 

 logical. Under the former head were ranged the callosities on the 

 inner side of the fore and hind limbs of the Horse its bushy tail, 

 its peculiar larynx, its short ears, and broad hoofs ; under the latter 

 head, the fact that the offspring of the horse with any of the allied 

 species is a hybrid, incapable of propagation with another mule, was 

 particularly mentioned. 



Leaving open the question whether the physiological distinction 

 just mentioned is, or is not, a universal character of species, it is 

 indubitable that it obtains between many species, and therefore has 

 to be accounted for by any theory of their origin. 



The species Equus caballus, thus separated from all others, is the 

 centre round which a number of other remarkable phenomena are 

 grouped. It is intimately allied in structure with three other mem- 

 bers of the existing creation, the Hyrax, the Tapir, and the Rhino- 

 ceros ; and less strait, though still definite, bonds of union connect it 

 with every living thing. Going back in time, the Horse can be 

 traced into the Pliocene formation, and perhaps it existed earlier 

 still ; but in the newer Miocene of Germany it is replaced by the 

 Hippotherium, an animal very like a true Equus, but having the two 

 rudimental toes in each foot developed, though small. Further back 

 in time, in the Eocene rocks, neither Equus nor Hippotherium have 

 been met with, nor Rhinoceros, Tapirus, nor Hyrax ; but, instead of 

 them, a singular animal the Palaotherium, which exhibits certain 

 points of resemblance with each of the four existing genera, is found. 



