138-(108) GRADATION IN ANIMAL LIFE. 



rapidity of such development, indicates low rank. The 

 very low inf usorians in stagnant water are fully matured 

 in a few days, or even hours ; most vertebrates require 

 from one to three years, while man asks from fifteen to 

 twenty years of adolescence. 



Individuality is a sign of superior rank ; such organ- 

 isms as sponges, (?) corals, and compound ascidians, are 

 low by reason of their lack of individual differentiation. 

 It is true that there are generally in such cases recogni- 

 zable units of organization, composing the common mass ; 

 we may, for instance, count the mouths present in a lump 

 of coral flesh ; yet these units pass into each other, or 

 into a mass of common flesh, without any boundary 

 lines. 



Fixity in one place, is a mark of low grade ; freedom 

 of locomotion, is a mark of superiority. Thus the star- 

 fish being free to move, is thereby much superior to the 

 crinoid that is immovably fixed. Fixity is too nearly al- 

 lied to vegetative life to rank high in an animal. The 

 sea-anemone is thus lower than the free-swimming jelly- 

 fish. 



Many animals are fixed in early life, and free-swim- 

 ming afterwards. This is true of many jelly-fishes, and 

 it is in harmony with the first law of development. Yet 

 some, like the sprat or embryo of the oyster, are free and 

 lively swimmers in their earliest days, but finally anchor 

 themselves permanently to some rock or shell. This is 

 one of the manifest exceptions to the first mentioned 

 law. 



The possession of a high degree of constructive skill, 

 or of capacities showing a high degree of either instinct 

 or intelligence, is of course indicative of high rank. 

 Wherever it is possible for us to recognize an intelli- 

 gence going beyond mere inherited instinct, it is evidence 

 of elevation in grade. Those animals that can easily be 

 taught new ways and new habits, over and above their 

 instinctive habits, stand higher than the multitude, that 

 can never get beyond the work of instinct, however elab- 

 orate this may be. 



There are many other signs of rank, many of which I 

 must omit, but a few more deserve passing mention. 



Parasites, sucking elaborated digested fluids from 

 the bodies of other animals, are always, for this reason, 



