VITAL ACTION VS. NATURE-ACTION 191 



course of ages, into classes, orders, and families, and 

 some of them, it may be, into a great number of spe- 

 cies, or varieties, which differ among themselves in 

 minor details of size, form, and color, or in their mode 

 of action. But even when subjected to widely differ- 

 ent external environments, for many millions of years, 

 the basic structural plans, the modes of growth, and 

 the vital processes peculiar to the larger classes never 

 change. Hence it is clear that material constitution 

 and architectural plans may have great stability and far 

 more influence in determining the character of lineal 

 descendants than any events likely to take place in the 

 world external to them. 



All these side branches to the great tree of evolu- 

 tion, these divergent types of structure and modes of 

 growth, with many of which nature has been experi- 

 menting since the very earliest recorded periods, have 

 either ended in defeat, or are doomed to defeat, in 

 the sense that they are themselves forever excluded 

 from attaining the highest phases of organic develop- 

 ment; although they may serve and have served as con- 

 structive agents, or as subsidiary aids, to a higher evo- 

 lution along other lines. 



Some leads have been fruitful, as the octopus, the 

 ant, and the bee. For a while, their progress in struc- 

 tural and psychic evolution was rapid and promising, 

 but they soon reached the fulness of their possibilities, 

 and their further progress now appears to be definitely 

 limited. The different types of structure represented 

 respectively by the oyster, the snail, the worm, and by 

 other less familiar forms, began their periods of trial 

 many millions of years before the first fish-like verte- 



