PROFESSOR OWEN ON THE AYE-AYE. Oa 
Applying to the Aye-aye the illustration of his hypothesis, as submitted by Mr. Darwin 
to the Linnean Society’, it may be admitted that the organization of a Lemur, feeding 
chiefly on fruits or birds, but sometimes on grubs, is, or might become, slightly plastic, 
in the sense of being subject to slight congenital variations of structure. We may, also, 
suppose changes to be in progress in the woods of Madagascar, causing the number of 
birds to decrease, and the number of insects to increase, especially of those the larvze of 
which are xylophagous. The effect of this might be that the Lemur would be driven to 
try to catch more grubs. His organization being slightly plastic, those individuals 
with the best hearing, the largest front incisors, and the slenderest middle digit, let the 
difference be ever so small, would be to that extent favoured, would tend to live longer, 
and to survive during that time of the year when birds or fruits were scarcest ; they 
would also rear more young, which would tend to inherit these slight peculiarities. 
Were the Lemurs to be reduced to this insect-food, those individuals less plastic than 
the incipient Aye-aye, or not varying in the same way, would become extinct. 
The varieties of condition of the human mind are manifold, and may be exemplified by 
the fact that there are some with modes and habits of thought which lead them to 
entertain no more doubt that such causes, in a thousand generations, would produce a 
marked effect upon the Lemurine dentition and limbs, adapting the form and structure 
of the Quadrumane to the catching of wood-boring grubs instead of birds, than that any 
domesticated quadruped can be improved by selection and careful breeding ; whilst to 
other minds the propounding of such plastic possibilities leaves no sense of any 
knowledge worth holding as to the origin of the species called Chiromys madagascariensis, 
no help to the conception of such origin which is at all equivalent to so wide a departure 
from actual experience of facts. We know of no changes in progress in the Island of 
Madagascar, necessitating a special quest of wood-boring larve by small quadrupeds of 
the Lemurine or Sciurine types of organization. Birds, fruits, and insects abound there 
in the ordinary proportions ; and the different forms of Lemuride coexist, with their 
several minor modifications, zoologically expressed by the generic terms Lichanotus, 
Propithecus, Chirogaleus, Lemur, and, we may now confidently add, Chiromys. 
That organic species are the result of still operating powers and influences is probable, 
from the great paleontological fact of the succession of such so-called species from 
their first appearance in the oldest-known fossiliferous strata: it is the more probable, 
from the kind and degree of similitude between the species that succeeds and the 
species that disappears, never to return as such ; the similitude being, in the main, of a 
nature expressed by the terms of ‘‘ progressive departure from a general to a special 
type.”” Creation by law is suggested by the many instances of retention of structures 
in palzozoic species which are embryonal and transitory in later species of the same 
order or class; and the suggestion acquires force by considering the analogies which 
the transitory embryonal stages in a higher species bear to the mature forms of lower 
* Proc. Linn. Soe. August 1858, p. 49. 
