Fig. 21. The Margin of the Equatorial Eain-Forest in North Borneo. Where- 

 ever this type of forest occurs it shows similar density (see Fig. 22), a fact 

 which explains the existence of so many purely arboreal animals (cf. Figs. 23 

 and 32) which spend their whole lives among the trees. (Photo hyH.M. Lomas. ) 



