WHAT IS LIFE? 61 



the disc which had been many hours separated from 

 the animal. The fringe does no more when the animal 

 is vigorous on the warm surface of the tranquil sea ; 

 it does no less now that the animal is in shreds. Look 

 in that saucer, and you will observe the fragment of 

 another Medusa ; the animal is dead, and almost melt- 

 ed away. I have already cut out two of the ovarial 

 chambers, yet you see the oval tentacles are twisting 

 about as if seeking prey. This is not ciliarity, but 

 contractility. This is life, unless you restrict the term 

 life to the meanino- it carries in its hio-hest formula. 

 If it is motion, it is vital motion. 



Can motion, alone, be taken as the index of life ? 

 Certainly not. But let us try to be precise in our 

 language. Life is a complex term, indicating complex 

 phenomena. In its highest formula, expressing all the 

 requisite generality of what is included in the term, it 

 indicates the triple unity of Nutrition, Reproduction, 

 and Decay. An animal grows, reproduces, and dies ; 

 these are the three capital and cardinal facts of its 

 organism. Out of these issue many derivative and 

 secondary phenomena, one of which is Motion. In 

 some animals, motion can scarcely be said to have 

 any existence. The Ascidians, for example, although 

 of rather complex structure, have nothing which ap- 

 proaches it, unless we should so designate the occa- 

 sional contraction and dilatation of their two orifices. 

 We may therefore conceive Life without Motion, and 

 Motion without Life ; and thus, with some plausi- 

 bility, ask whether the movements exhibited by the 



