240 NUTS AND NUTTING. 



able not merely to pick them with tlu ir hands and 

 crack them with their teeth, but even to use a 

 large stone as a hammer to force them open. For 

 this reason, in tropical countries we find some 

 trees, like the cocoa-nut. palm, which produce ex- 

 tremely large and hard nuts sufficient to baflle in 

 many cases the clever monkeys themselves. Yet 

 even the cocoa-nuts are rifled by the cocoa-nut 

 crab, who hiserts his pincers through one of the 

 three holes or pores at the top of the nut, and 

 slowly extracts the nutritious kernel piecemeal. 

 There are other tropical kinds, such as the Brazil 

 nut, which have a double shell, the outer one 

 being large and round, like the cocoa-nut, and en- 

 closing within it the smaller roughly triangular 

 nuts with whose irregular shapes we are all so 

 familiar on our own dinner-tables. The queer 

 corners of the Brazil nuts are of course due to 

 their being all squeezed up against one another as 

 they grow inside the large surrounding outer 

 shell. The toucans and hornbills, the huge fruit- 

 bats, the opossums, and the numerous big tropical 

 s(iuirrels have all, no doubt, borne their own sub- 

 sidiary part in the development of the large 

 and hard-shelled southern nuts. For, as only the 

 nuts that do not get cracked can survive to grow 

 u[) into ti'ces from one generation to another, all 

 the softer forms get quickly weeded out by the 

 constant selective action of the nut-eating animals. 



