THE GIBBONS 63 



THE; Wou-Wou, OR SILVER GIBBON {Hylobates leutiscus) 



The gray or silver gibbon, or wou-wou, a name often incorrectly applied to 

 the agile gibbon, comes from the island of Java, and most zoologists agree in re- 

 garding it as a distinct species. It is characterized by its general ashy or bluish- 

 gray color, the presence of a large square black patch on the top of the head, and 

 also by the white or gray fringe of hair surrounding the blackish face. The fur also 

 appears to be longer, thicker, and of a more woolly nature than is the case in the 

 other species, and the color is stated to be usually lighter on the under parts than 

 on the back. Specimens of both this and the preceding species have been exhibited 

 in the I,ondon Zoological Society's Gardens. 



FOSSIL GIBBONS 



In the explorations which have been conducted in the caves of Borneo, remains 

 of gibbons, probably belonging to species still existing in the same regions, have 

 been met with in a subfossil condition. This is only what we should naturally 

 have expected to be the case. Very different, however, is the occurrence of fossil 

 gibbons in fresh-water strata belonging to the middle portion of the Tertiary period 

 in France and Switzerland ; for it is quite certain that these animals could not have 

 existed in a climate at all approaching that now characterizing Europe. We shall, 

 therefore, be safe in assuming that, at the period in question, portions of Southern 

 Europe were clothed with dense forests, growing in a hot and moist climate closely 

 resembling that of the Malay Archipelago of the present day. The evidence for the 

 former prevalence of this tropical European climate does not, however, rest solely on 

 the fossil gibbons, since many of the other animals found in the same strata are very 

 similar to those now characteristic of the warmer regions of the East ; while the 

 presence of palms, resembling those of tropical regions, as well as other plants, sup- 

 plements the evidence of the animals in a manner which must be convincing to all 

 who pay any attention to the subject. After the middle or miocene division of the 

 Tertiary period we have no evidence of the existence of gibbons in any part of Eu- 

 rope, although many kinds of monkeys were abundant until much later. 



