THE GREEN CRAB. 129 



with a good pocket lens, the eyes are seen to be com- 

 pound, i.e. formed of a great number of facets, each, 

 possessing the power of vision, and all communicating 

 with their common optic nerve. The delicate raised 

 lines caused by the serried ranks of these compound 

 eyes are the origin of the peculiar lustre just mentioned. 

 It will be seen, too, that the visual portion of these 

 organs passes partially roimd the footstalks, so that 

 when the creature protrudes its eyes it can see objects on 

 all sides with equal ease. 



Now replace the crab in the water, and watch it as 

 it exhibits the instinct which has been implanted in its 

 being by its divine Creator. 



Advancing with the flowing tide, and ever remain- 

 ing within a foot or two of the edge, the crab keeps its 

 eager wat<;h for food, and suffers few living things to 

 pass without capturing them. The whole nature of the 

 animal seems to be changed while it is seeking its prey. 

 The timid, fearful demeanour which it assumes when 

 taken at a disadvantage wholly vanishes, and the appa- 

 rently ungainly crab becomes full of life and spirit, 

 active and fierce as the hungry leopard, and no less 

 destructive among the smaller beings that frequent the 

 same locality. 



Now does it shew the ubiquitous advantages of its 

 singular mode of progression. Let a tiny fish, a smaller 

 crustacean or a soft mollusc, pass it within reasonable 

 distance, and the crab darts at it with a tiger-like 

 energy, and seldom fails to secure its prey. I have seen 



