Chap. V. DEPARTURE FROM CARirf. 211 



of these is a veritable colossus, the Hister maximus of 

 Linngeus. A third group (Hololeptse) are found only 

 under the bark of trees ; their heads are not retractable 

 within the breast, and their bodies are excessively de- 

 pressed, to fit them for living in narrow crevices, 

 some kinds being literally as thin as a wafer. A 

 fourth set of species (Tryi^anaeus) form a perfect con- 

 trast to these, being cylindrical in shape. They drill 

 holes into solid wood, and look like tiny animated 

 gimlets when seen at work, their pointed heads being 

 fixed in the wood whilst their smooth glossy bodies 

 work rapidly round, so as to create little streams of 

 sawdust from the holes. Several families of insects 

 show similar diversities of adaptation amongst their 

 species, but none, I think, to the same extent as the 

 Histeridae, considering the narrow limits of the group. 

 The facts presented by such groups in the animal 

 kingdom must be taken into account in any explana- 

 tion of the way the almost infinite diversity of the forms 

 of life has been brought about on this wonderful earth. 



At length, on the 12th of February, I left Caripi, 

 my Negro and Indian neighbours bidding me a warm 

 " adeos." I had passed a delightful time, notwithstand- 

 ing the many privations undergone in the way of food. 

 The wet season had now set in ; the low lands and 

 islands would soon become flooded daily at high water, 

 and the difficulty of obtaining fresh provisions would 

 increase. I intended, therefore, to spend the next three 

 months at Para, in whose neio-hbourhood there was still 

 much to be done in the intervals of fine weather, and 

 then start off on another excursion into the interior. 



p2 



