PROFESSOR OWEN ON THE AYE-AYE. 93 
operation of secondary laws in a ‘ world accursed,’ have had degenerate successors ; 
and the departures from type, varying according to the diversity of deteriorating 
influences, are represented by the majority of the naturalist’s species of the present day. 
Applying his principle to those he had treated of in his great ‘ Histoire Naturelle’,’ 
Buffon believed that he was able to reduce them to fifteen primitive stocks. ‘The theory 
of ‘ degeneration’ assumes a course of change inversely to that of ‘ derivation’; which, 
moreover, rigidly excludes the operation of any cause, not in the actual category of 
powers, of the origin of the parent forms of organic beings. I will not occupy time in 
attempting to show how the ‘ degeneration-hypothesis ’ could have operated in producing 
the various remarkable correlated structures in the organization of the Aye-aye: it 
might have been regarded by Buffon as a primitive type, or an ‘isolated form.’ 
According to the modifying influences suggested by Lamarck, a Lemurine quadruped, 
attracted by the noise of a boring caterpillar in the bough on which it happened to be 
perched, instinctively applied its incisors to the bark, and, by frequent repetition of such 
efforts, increased the mass of the gnawing muscles ; which, stimulating the growth of 
the bone, led to concomitant modifications in the size and proportion of the jaws. The 
incisors, by repeated pressure, either became welded into a single pair above and below ; 
or, the stimulus to excessive growth being concentrated on one incisor, the neighbouring 
teeth became atrophied by disuse, and by derivation of their nutrient fluid to the 
contiguous pulp ; hence the preponderating size of the pair of front teeth, and the 
extent of edentulous space behind them. Concomitantly with the efforts excited by the 
particular larvivorous tendency of a certain Madagascar Lemur to expose the canal in 
which its favourite morsel lay hidden, were repeated endeavours to poke the longest 
finger into the burrow so laid open. The repeated squeezing of the soft skin, with the 
compression of the nerves and vessels, permanently affected the growth of such digit, 
and kept it reduced to the blighted state, whereby it happens to be suited to the work 
of extracting the larva. Lamarck supposes all these changes to be gradual, and 
effected only through long succession of generations; he assumes that changes of 
structure, due to habitual efforts and actions, are transmissible to offspring ; and he 
finally invokes, like his successors, the requisite lapse of time and long course of 
generations. It is to be supposed that, until the modifications of dental and digital 
structures were brought about, the grub-hunting Lemur subsisted on the necessary 
proportion of fruits and other food more readily obtainable under the ordinary Lemurine 
conditions of existence. 
That the same finger should be the seat of the wasting influences on both 
hands, and in all Aye-ayes, strikes one as a result hardly to be looked for on the 
hypothesis of the cause of such specific structures propounded by Lamarck: that there 
should be a modification of the muscles of the forearm, whereby both fleror sublimus 
and flecor profundus combine their action upon the same tendon, pulling the probe- 
* Tome xiv. p. 311. 
