108 CARIP! AND THE BAY OF MARA/JO. Cuap. V. 
dung; most of these are somewhat cubical in shape, the head being 
retractable within the breastplate, as in the tortoise. Another group 
of Histeridz are much flatter in form, and live in the moist interior 
of palm-tree stems; one of these is a veritable colossus, the Hister 
maximus of Linneus. A third group (Hololeptz) are found only under 
the bark of trees ; their heads are not retractable within the breast, and 
their bodies are excessively depressed, to fit them for living in narrow 
crevices, some kinds being literally as thin as a wafer. A fourth set of 
species (Trypanzeus) form a perfect contrast 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 Histeridz, considering the narrow 
limits of the group. The facts presented by such groups in the animal 
kingdom must be taken into account in any explanation 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, notwithstanding the many privations undergone in 
the way of food. The wet season had now set in; the lowlands 
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 neighbour- 
hood there was still much to be done in the intervals of fine weather, 
and then start off on another excursion into the interior. 
