Prof, Owen on the Aye-Aye. 483 
spirit, afforded the means of a minute external description, The 
extremities were described as follows :—‘‘The fore leg turns freely 
in the prone and supine position; it is pentadactyle: the inner- 
most digit stands out at an acute angle with the index, and is op- 
— to the other digits, making a prehensile hand, but in a 
ess perfect degree than in the old-world or ‘catarrhine’ quadru- 
mana. The second, fourth, and fifth digits have the iatrvoae | thick- 
ness, the fourth being almost twice the length of the second. The 
third or middle finger is singularly attenuated, is rather shorter than 
the fourth digit, and is terminated by a slender curved claw. It is 
this seemingly atrophied digit which the Aye-aye inserts into the 
burrows of the wood-boring caterpillars, after it has gnawed down to 
and exposed them by its strong fore teeth, in order to extract the 
grub. The hind limb is longer than the fore limb, and is terminated 
by a more perfect hand-—the ‘ hallux’ or thumb being stronger, 
and set at a more open angle with the other toes, and these being 
more similar to each other in length and thickness: the thumb hag 
a flat, broad nail.’’ Prof. Owen observed that, from the external cha- 
racters of the Aye-aye, it might be inferred that it was of arboreal 
habits, the limbs being constructed chiefly for grasping, especially the 
hinder pair, as in all good climbers. The circular open eye, large 
iris, and wide pupil, reducible to a minute point when contracted, 
indicated a climber of nocturnal habits. The large and perfect ears 
bespoke the acuteness of their sense. The tail, long and bushy, but 
not prehensile, might add to the protective non-conducting covering 
of the well-clothed body during sleep. Prof. Owen then proceeded 
to describe the skeleton of the Aye-aye. 
January 28, 1862.—Dr. J. E, Gray, F.R.S., V.P., in the Chair. 
Professor Owen concluded the reading of his memoir on the Aye- 
aye (Chiromys madagascariensis), which had been adjourned from 
the last meeting of the Society. The portions of the structure of 
this animal successively examined were the dentition, the muscles, 
the brain, the digestive organs, the organs of circulation and respira- 
tion, and the renal and genital organs. The author then proceeded 
to the comparison of its external characters, its osteology, and its in- 
ternal structure with those of the Lemurs and Rodents, and showed 
that in a variety of particulars its nearest approach was to members 
of the lemurine group. In ordinary zoological or external characters 
its nearest allies were certain Galagos of Africa (Otolicnus crassi- 
caudatus and O. Alleni). In conclusion, he entered into the evi- 
dence afforded by the peculiarities of this animal on the question of 
the origin of species, and, after showing the arguments in favour o 
the derivative hypothesis and those against its mode of operation, as 
propounded by Buffon, Lamarck, and Darwin, came to the conclu- 
sion that, whilst the general evidence on this subject was in favour 
of creation by law, he was compelled to acknowledge ignorance as 
to the mode in which such secondary causes might have operated 
in the origin of Chiromys. At the same time he fully admitted that 
the attempts to dissipate the mystery which environed the origin of 
species, whether successful or not, could not but be fraught with 
great collateral advantages to zoological science, 
