HOMOLOGIES. 203 



them, I would nevertheless attempt to do it, in 

 order to show how the countless forms of animal 

 life have been generalized into the few grand, 

 but simple intellectual conceptions on which all 

 the past populations of the earth as well as the 

 present creation are founded. In such attempts 

 to divest the thought of its material expression, 

 especially when that expression is multiplied in 

 such thousand-fold variety of form and color, our 

 familiarity with living animals is almost an obsta- 

 cle to our success. For I shall hardly be able to 

 allude to the formula of the Radiates, for in- 

 stance, the abstract idea that includes all the 

 structural possibilities of that division of the An- 

 imal Kingdom, without recalling to my read- 

 ers a Polyp or a Jelly-Fish, a Sea-Urchin or a 

 Star-Fish. Neither can I present the structural 

 elements of the Mollusk plan, without reminding 

 them of an Oyster or a Clam, a Snail or a Cuttle- 

 Fish, or of the Articulate plan, without calling 

 up at once the form of a Worm, a Lobster, or an 

 Insect, or of the Vertebrate plan, without 

 giving it the special character of Fish, Reptile, 

 Bird, or Mammal. Yet I insist that all living 

 beings are but the different modes of expressing 

 these formulae, and that all animals have, within 

 the limits of their own branch of the Animal 

 Kingdom, the same structural elements, though 

 each branch is entirely distinct. If this be true, 



