Camouflage 193 



and by the flexibility of their joints to perform this 

 operation. Then the animal selects a suitable object 

 and holds the broken portion to the appendages of its 

 mouth where it is manipulated and covered with a secre- 

 tion of some adhesive substance, after which it is car- 

 ried with an overhand movement to the back and at- 

 tached. This is continually repeated until within a few 

 hours the spider crab once more resembles a miniature 

 garden. In addition to the cement they use, some crabs 

 are provided with hooks and barbs on their backs, 

 which aid in holding fast the transplanted organisms. 



It may be of further interest to note that among the 

 spider crabs are found the largest crustaceans in the 

 world. These are the giant Macrochiras of Japan, 

 full-grown individuals of which are said to have a leg 

 spread measuring fifteen feet. 



The invisibility that the dwellers of the tide pool 

 achieve by color combinations, strange shapes, or mask- 

 ing would seem to be perfect, at least to human eyes — 

 and there is no good reason to believe that the lower 

 animals have a better vision or even one to equal ours. 

 Yet, perfect as is this achievement, it is as nothing, 

 in a way of speaking, compared with that of some crea- 

 tures in this place, which dispense entirely with such 

 shifts. The glass prawn {Palcemonetes vulgaris) is 

 such a one. This crustacean frequently crowds the 

 pool in great numbers, especially in the fall; but so 

 transparent is it that shoals containing hundreds 

 could pass within the observer's reach without his 

 once suspecting it. Only by holding it to the light 

 in a glass of water can its form be seen with any 

 degree of distinctness. Its body is about one and 



