208 THE STUDY OF ZOOLOGY vii 



what naturalists term the sub-kingdom Ccelcnterata, 

 would have grouped themselves around my type ; 

 had a snail been chosen, the inhabitants of all 

 univalve and bivalve, land and water, shells, the 

 lamp shells, the squids, and the sea-mat would 

 have gradually linked themselves on to it as mem- 

 bers of the same sub-kingdom of Mollusca ; and 

 finally, starting from man, I should have been com- 

 pelled to admit first, the ape, the rat, the horse, 

 the dog, into the same class ; and then the bird, 

 the crocodile, the turtle, the frog, and the fish, 

 into the same sub-kingdom of Vertelrata. 



And if I had followed out all these various lines 

 of classification fully, I should discover in the end 

 that there was no animal, either recent or fossil, 

 which did not at once fall into one or other of 

 these sub-kingdoms. In other words, every animal 

 is organised upon one or other of the five, or more, 

 plans, the existence of which renders our classifi- 

 cation possible. And so definitely and precisely 

 marked is the structure of each animal, that, in 

 the present state of our knowledge, there is not 

 the least evidence to prove that a form, in 

 the slightest degree transitional between any of 

 the two groups Vertebrata, Annulosa, Mollusca, 

 and Ccelenterata, either exists, or has existed, 

 during that period of the earth's history which is 

 recorded by the geologist. 1 Nevertheless, you 

 must not for a moment suppose, because no such 



f 1 The different grouping necessitated by later knowledge 

 does not affect the principle of the argument. 1894.] 



