15 



modified. But does the formula which expresses the es- 

 sential 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 protoplasm with a nucleus. There 

 are sundry very low animals, each of which, structurally, 

 is a mere colorless blood-corpuscle, leading an independ- 

 ent life. But, at the very bottom of the animal scale, 

 even this simplicity becomes simplified, and all the phe- 

 nomena of life are manifested by a particle of proto- 

 plasm 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 sim- 

 plest 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 to- 

 gether. And in ancient times, no less than at the pres- 

 ent day, such living beings as these have been the great- 

 est of rock builders. 



What has been said of the animal world 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 examination further proves 

 that the whole substance of the nettle is made up of a 

 repetition of such masses of nucleated protoplasm, eacli 

 contained in a wooden case, which is modified in form, 

 sometimes into a woody fibre, sometimes into a duct 

 or spiral vessel, sometimes into a pollen grain, or an 

 ovule. Traced back to its earliest state, the nettle arises 



