94 PROFESSOR OWEN ON THE AYE-AYE. 
like digit, is left unaccounted for. The physiologist finds still more difficulty in 
accepting the explanation of the way in which the peculiar conditions of the incisors 
could be brought about. The action of muscles pressing upon the bony sockets might 
affect the growth of teeth filling such sockets, but could not change a tooth of limited 
growth, like the incisors of an ordinary Lemur, into a tooth of uninterrupted growth. 
Besides, the crowns of both the scalpriform incisors of the Ciiromys and the ordinary 
small incisors of other Lemurines are formed according to their specific shape and size 
before they protrude from the gum. ‘They acquire so much development while the 
animal still derives its sustenance from the mother’s milk. In the Aye-aye the chisel 
or gouge is prepared prior to the action of the forces by which it is to be worked. The 
great scalpriform front teeth thus appear to be structures fore-ordained—to be pre- 
determined characters of the grub-extracting Lemur ; and one can as little conceive the 
development of these teeth to be the result of external stimulus or effort, as the develop- 
ment of the tail, or as the atrophy of the digitus medius of both hands. I have, on a 
former occasion, tested the Lamarckian hypothesis of transmutation by the phenomena 
of the dentition of the male Gorilla’, and have not yet seen a refutation of my argument. 
A strong superorbital ridge may project, as an occasional variety, in Man; and may be 
supposed to exemplify the way in which, on the degeneration-hypothesis, Man might 
sink into the Ape. But such a fact in no way affects the physiological conclusions 
against the Lamarckian doctrine of transmutation. 
There remains, then, to be seen whether the subsequently propounded hypothesis of 
‘natural selection’ will afford us a better or more intelligible view of the origin of the 
species called Chiromys madagascariensis. 
I may remark, on the outset, that this hypothesis differs from Lamarck’s in invoking 
a supernatural commencement of organisms which are held to have been ‘‘ descended 
from some one primordial form, into which life was first breathed”’*. And herein is 
one main distinction between it and the ‘ derivative hypothesis,’ which maintains that 
single-celled organisms, so diversified as to be relegated to distinct orders and classes 
of Protozoa, are now, as heretofore, in course of creation, or formation, by the ordained 
potentiality of second causes; with innate capacities of variation and development, 
giving rise, in long course of generations, to such differentiated beings as may be 
distinguished by the terms ‘ plant’ and ‘animal ;’ from which all higher animals and 
plants have, through like influences, ascended, and are being ascensively derived. 
This, as the naturalist knows, is mere hypothesis, at present destitute of proof. But 
it is more consistent with the phenomena of life about us, with the ever-recurring 
appearance of mould and monads, and with the coexistence, at the present time, of all 
grades of life rising therefrom up to Man, than is the notion of the origin of life which 
is propounded in Mr. Darwin’s book ‘ On the Origin of Species by Natural Selection.’ . 
* Trans. Zool. Soc. vol. iii. p. 381, and vol. iv. p. 175. See also ‘Classification of the Mammalia,’ 8yo, 
P P 
1859, p. 101. * Darwin, ‘On the Origin of Species,’ p. 414. 
