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 NatureUe\' 

 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, v;herehY both flexor sublimus 

 and flexor profundus combine their action upon the same tendon, pulling the probe- 



' Tome xiv. p. 311. 



