HI ON THE PHYSICAL BASIS OF LIFE 141 



tion further proves that the whole substance of 

 the nettle is made up of a repetition of such masses 

 of nucleated protoplasm, each contained in a 

 wooden case, which is modified in form, some- 

 times 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 as the man does, in a particle 

 of nucleated protoplasm. And in the lowest 

 plants, as in the lowest animals, a single mass 

 of such protoplasm may constitute the whole 

 plant, or the protoplasm may exist without a 

 nucleus. 



Under these circumstances it may well be asked, 

 how is one mass of non-nucleated protoplasm to 

 be distinguished from another ? why call one 

 " plant " and the other "animal " ? 



The only reply is that, so far as form is con- 

 cerned, plants and animals are not separable, and 

 that, in many cases, it is a mere matter of con- 

 vention whether we call a given organism an 

 animal or a plant. There is a living body called 

 \SihaMum septicum, which appears upon decaying 

 vegetable substances, and, in one of its forms, 

 is common upon the surfaces of tan-pits. In this 

 condition it is, to all intents and purposes, a 

 fungus, and formerly was always regarded as 

 such ; but the remarkable investigations of De 

 Bary have shown that, in another condition, the 

 is an actively locomotive creature, and 



