A REMARKABLE MAMMAL 185 
wood till it opens up the tunnel of the burrowing 
larva. As soon as the tunnel is reached the attenuated 
middle finger is thrust in, either to act as a probe to 
determine the position of the larva, or to drag it out from 
its hiding-place, or perhaps for both purposes. Some un- 
certainty still obtains as to the exact details of these and 
other operations of a like nature, for our information on 
these points appears to be mainly, if not exclusively, based 
on native accounts. There is, however, little doubt that 
the modus operandi is in the main as described above. 
We thus have a sufficient and satisfactory explanation 
of the reason why the aye-aye differs so remarkably in its 
dentition and in the structure of its hand from all its living 
kindred. If, however, we attempt to account for the gradual 
development of these peculiarities by what is commonly called 
natural selection, we encounter considerable difficulty. It is 
easy to conceive how the ancestors of the horse lost their 
lateral toes by disuse, but how an ancestral aye-aye gradually 
reduced the size of its middle finger till it assumed the 
attenuated proportions of its existing representative is very 
hard to understand, seeing that a slight diminution in the 
calibre of this digit would be of little or no advantage. 
Some much more potent cause than “natural selection” 
seems necessary in this, as in many other instances, 
As regards its general mode of life, the aye-aye wanders 
through the silent forest at night in pairs, and never appears 
to associate with others of its fellows than its partner. Pro- 
bably the partnership is for life, but on this point we have 
no definite information. The aye-aye is one of the com- 
paratively few mammals which build a regular nest; this 
being constructed, according to Mr. Baron, of the carefully 
rolled up leaves of one particular kind of tree, and lined 
with small twigs and dry leaves; the whole structure having 
