102 SKETCHES OF CUE ATI OX. 



we are indebted to the genius of George Cuvier — that I 

 wish to impress. Suffice it to say that all animals are either 

 vertebrated — possessed of a backbone ; articulated — with an 

 external horny crust, composed of rings, like insects, lob- 

 sters, and worms ; molluscous — with soft bodies like slugs, 

 very often covered by a shell, like snails and oysters ; or 

 radiated — with bodies composed of parts somewhat sym- 

 metrically arranged on all sides with reference to the cen- 

 tre, like the starfish and corals. I have named the most 

 striking character which distinguishes each of these great 

 branches of the animal kingdom. All the other parts con- 

 form to these ; indeed, the basis of each peculiar plan is laid 

 in the nervous system, at a very early period of embryonic 

 development ; and the hard parts — the bones and external 

 crust — are moulded to this, so that, though the real basis 

 of these distinctions is hidden from view, the external form 

 and proportions become always an infallible exponent of 

 the fundamental plan. 



Three of these fundamental plans are called into requisi- 

 tion in the constitution of the very first population of our 

 globe, omitting any consideration of the little-known ex- 

 istences of the Eozoic Time. The coral was a radiate ; the 

 Lbigida was a mollusc ; the trilobite was an articulate. 

 The fourth plan was drawn upon before the close of the 

 first great period of animal history, and was realized in the 

 form of a fish. 



In the very first chapter of the book of Nature, then, we 

 read the announcement of a programme which is still in 

 process of execution. The type of the primeval coral has 

 sprouted into the sea-anemone, the sea-nettle, and the star- 

 fish. The type of the Lingida has been degraded into the 

 Bryozoan and nummulite, and expanded into the clam, the 

 snail, and the cuttle-fish. The type of the trilobite has 

 varied into the worm below and the insect above ; while 



