CONSTITUTION OF THE ANIMAL AND PLANT KINGDOMS. 45 



confines of the animal world, and entering into the domain of the 

 quadrupeds or mammals, at the head of which latter group stands 

 the human subject, we find the type of fish, frog, reptile, and bird 

 to be accurately adhered to as the fundamental plan of the quadruped 



d 



FIG. 9. ZOOPHYTES 

 (b and d represent portions of a and c, magnified). 



body itself; so that the diagram of the fish may be left to express 

 accurately and truly the broad outlines of human anatomy. In this 

 way we discover that a type of animals the Vertebrata first outlined 

 by Lamarck, as already noted, can be constructed on precisely the 

 same lines, and for the same structural 

 reasons that made the constitution of 

 the Articulate type a reality of living 

 nature. Fishes, frogs, reptiles, birds,* 

 and quadrupeds or mammals, includ- 

 ing man, thus possess bodies con- 

 structed on the same fundamental 

 type or plan. 



To continue the illustration of 

 the formation of natural groups or 

 " types" of animal life through the 

 discovery of broad or fundamental 

 correspondence in the structure of 

 the body, were an easy matter. It 

 may readily be shown that all ordin- 

 ary shell-fish such as the oysters, 

 cockles, snails, whelks along with 

 the sea-butterflies (Pteropoda\ and the cuttle-fishes form another 

 well-marked type, distinguished by the peculiar disposition of the 



FIG. io. JELLY-FISH. 



