SPECIES OF GIBBONS 
The tail is wanting, as in the highest apes and in man ; 
and the vermiform appendix is present as in the same. 
The lower monkeys generally (but not always) possess 
a tail. So much then for the chief points in the inward 
and outward structure of the Hoolock and its congeners 
which help to fix its place in the Simian system. The 
hoolock, or at least some form of gibbon, is almost sure 
to be on view in the New Ape House at any given time. 
It will probably also appeal to another sense, that of 
hearing; for this gibbon, like others, has a piercing 
though not unpleasant voice by means of which it utters 
a series of cries which have been variously rendered 
“ Hooloo”’ and “ Whoko.” It prefers climbing to 
walking ; and when it does walk, which in nature 
appears to be practically never, it walks on two legs 
as a rule, and divaricates its big toe like unbooted 
man. Its extraordinarily long arms are used in this 
method of progression as balancing poles to aid in 
its waddling run. Placed on a tree the gibbon has no 
equal among the monkey tribe. It swings from 
bough to bough “with the unerring accuracy of a 
finished trapeze performer.’ It is an odd thing that 
this gibbon at any rate cannot swim, and naturally, 
therefore, never takes to the water on its own account. 
Monkeys, as a rule, can, and do voluntarily, set out to 
swim, crossing rivers in their marches, but the gibbon 
never; and thus its range is often limited by great 
rivers such as the Irrawaddy. In this dislike of water 
it plainly resembles man, who is almost the only other 
creature that cannot swim by the light of nature, but 
requires teaching. The specimens of gibbon that 
have been on view at the Zoo are numerous, and are 
of many species. Quite recently there was on view 
an example of the very rare Hainan gibbon, an ape 
which frequents the island of Hainan, its easterly limit 
as a genus. Another rarity is the Siamang, a gibbon 
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