140 
THE DESCENT OF HAN. 
Part !■ 
branches until the rind is cracked, and then tear it off 
with the fingers of the two hands. Other monkeys open 
mussel-shells with the two thumbs. With their fingers 
they pull out thorns and burs, and hunt for each other’s 
parasites. In a state ol nature they break open hard 
fruits with the aid of stones. They roll down stones 
or throw them at their enemies ; nevertheless, they 
perform these various actions clumsily, and they are 
quite unable, as I have myself seen, to throw a stone 
with precision. 
It seems to me far from true that because “ objects 
“ are grasped clumsily ” by monkeys, “ a much less 
specialised organ of prehension ” would have served 
them 62 as well as their present hands. On the con- 
i' 1 1 try, I see no reason to doubt that a more perfectly 
constructed hand would have been an advantage to them, 
provided, and it is important to note this, that their 
hands had not thus been rendered less well adapted for 
climbing trees. We may suspect that a perfect hand 
would have been disadvantageous tor climbing; as the 
most aiboieal monkeys in the world, namely Ateles in 
America and Hylobates in Asia, either have their thumbs 
much 1 educed in size and even rudimentary, or their 
fingers partially coherent, so that their hands are con- 
verted into mere grasping-hooks . 63 
As soon as some ancient member in the great series 
of the Primates came, owing to a change in its manner 
of procuring subsistence, or to a change in the con- 
02 ‘ Quarterly "Review,’ April, 1869, p. 392. 
1,3 In llylobates syndactylus, as the name expresses, two of the digits 
regularly cohere ; and this, as Mr. Blytli informs me, is occasionally 
the case with the digits of H. agilis, lar, and leucisous. In Colobus the 
thumb is likewise deficient; these monkeys are strictly arboreal and 
extraordinarily active (Brehm, ‘ Tliierleben,’ B. i. s. 50), but whether 
they are better climbers or graspers than the species of the allied 
genera, I do not know. 
