140 OX THE PHYSICAL BASIS OF LIFE m 



in its earliest state, is a mere multiple of such 

 units ; and in its perfect condition, it is a multiple 

 of such units, variously modified. 



But does the formula which expresses the 

 essential structural character of the highest animal 

 cover all the rest, as the statement of its powers 

 and faculties covered that of all others ? Very 

 nearly. Beast and fowl, reptile and fish, mollusk, 

 worm, and polype, are all composed of structural 

 units of the same character, namely, masses of 

 f protoplasm with a nucleus. There are sundry 

 very low animals, each of which, structurally, is a 

 mere colourless blood-corpuscle, leading an inde- 

 pendent life. But, at the very bottom of the 

 animal scale, even this simplicity becomes simpli- 

 fied, and all the pha3nomena of life are manifested 

 by a particle of protoplasm without a nucleus. 

 Nor are such organisms insignificant by reason of 

 their want of complexity. It is a fair question 

 whether the protoplasm of those simplest forms of 

 life, which people an immense extent of the bottom 

 of the sea, would not outweigh that of all the 

 higher living beings which inhabit the land put 

 together. And in ancient times, no less than .it 

 the present day, such living beings as these have 

 been the greatest of rock builders. 



What has been said of the animal \\orM is no 

 less true of plants. Imbedded in the protoplasm 

 at the broad, or attached, end of the nettle hair, 

 there lies a spheroidal nucleus. Careful examina- 



