16 THE SURVIVAL OF THE UNLIKE. [l. 



vironment of the given individual or of its recent ances- 

 tors. Its evolution has been acephalic, diffuse, or head- 

 less, and the individual plant or tree has no proper con- 

 centration of parts. For the most part, it is filled with 

 unspecialized plasma, which, when removed from the 

 parent individual (as in cuttings and grafts), is able to 

 reproduce another like individual. The arrangements of 

 leaves, branches, the parts of the flower, and even of 

 seeds in the fruit, are thus rotate or circular, and in the 

 highest type of plants the annual lateral increments of 

 gi'owth are disposed in like fashion; and it is significant 

 to observe that in the compositfc, which is considered to 

 be the latest and highest general type of plant-form, the 

 rotate or centrifugal arranfjcment is most emphatically 

 developed. The circular arrangement of parts is the 

 typical one for higher plants, and any departure from 

 this form is a specialization, and demands explanation. 



The point I wish to urge, therefore, is the nature of 

 the obvious or external divergence of plant -like and ani- 

 iP3l-like lines of ascent. The significance of the bilateral 

 stniohire of animal -types is well understood, but this 

 significance has been drawn, so far as I know, from a 

 comparison of bilateral or dimeric animals v/ith rotate or 

 polymeric animals. I want to put a larger meaning into 

 it, by making bilateralism the symbol of the onward 

 march of animal evolution, and circumlateralisra (if I 

 may invent the term), the symbol of plant evolution. 

 The suggestion, however, applies simply to the general 

 arrangement of the parts or organs of the plant body, 

 and has no relation to structural characteristics and 

 relationships. It is a suggestion of analogues, not of 

 homologues. We may, therefore, contrast these two 

 great lines of ascent which, with so many vicissitudes, 



