PROFESSOR OWEN ON THE AYE-AYE. 95 



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 larvae 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 larvae 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 Lemurida coexist, v.nth their 

 several minor modifications, zoologically expressed by the generic terms lAchanotus, 

 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 palaeontological fact of the succession of such so-called species from 

 their first appearance in the oldest-known fossihferous 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 palaeozoic 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. Soc. August 1858, p. 49. 



