SIMPLEST FORMS OF VEGETABLE LIFE 53 



sarcode, has been appropriately designated by Professor Huxley ' the 

 physical basis of life.' In its typical state (such as it presents 

 among rhizopods) it is a semi-fluid, tenacious, glairy substance, 

 resembling alike in aspect and in composition the albumen (or 

 micoagulated * white ') of an unboiled egg. But it is fundamentally 

 distinguished from that or any other form of dead matter by two 

 attributes, which (as being peculiar to living substances) are desig- 

 nated vital: (1) its power of increase, by assimilating (that is, con- 

 verting into the likeness of itself, and endowing with its own pro- 

 perties) nutrient material obtained from without ; (2) its power of 

 spontaneous movement, which shows itself in an extraordinary variety 

 of actions, sometimes slow and progressive, sometimes rapid, some- 

 times wave-like and continuous^ and sometimes rhythmical with 

 regular intervals of rest. When examined under a sufficiently high 

 magnifying power, multitudes of minute granules are usually seen to 

 be diffused through it, which have been termed * microsoines.' 

 Protoplasm, whether living or dead, has a great power of absorbing 

 water; but the distinction between these two states is singularly 

 marked by its behaviour in regard to any colouring matter which the 

 w r ater may contain. Thus, if living protoplasm be treated with a 

 solution of carmine, it will remain unstained so long as it retains 

 its vitality. But if the protoplasm be dead, the carmine will at once 

 pervade its whole substance, and stain it throughout with a colour 

 even more intense than that of the solution ; thus furnishing (as 

 was first pointed out by Dr. Beale) a ready means of distinguishing 

 the * germinal matter,' or protoplasmic component of the tissues of 

 higher animals, from the ' formed material ' which is the most con- 

 spicuous part of their structure. 



All those minute and simple forms of life with which the micro- 

 scope brings us into acquaintance consist essentially of particles of 

 protoplasm, each kind having usually a tolerably definite size and 

 shape, and showing (at least in some stage of its existence) some- 

 thing distinctive in its habit of life. And it is rather according to 

 the manner in which they respectively live, grow, and multiply, 

 than on account of any structural peculiarities, that they are assigned 

 to the vegetable or to the animal kingdom respectively. It is 

 impossible, in the present state of our knowledge, to lay down any 

 definite line of demarcation between the two kingdoms ; since there 

 is no single character by which the animal or vegetable nature of 

 any organism can be tested. Probably the one which is most 

 generally applicable among those that most closely approximate to 

 one another is not, as formerly supposed, the presence or absence of 

 spontaneous motion, but, on the one hand, the dependence of the 

 organism for nutriment upon organic compounds already formed 

 which it takes (in some way or other) into the interior of its body, 

 or, on the other, its possession of the power of producing the organic 

 << impounds which it applies to the increase of its fabric, at the 

 expense of the inorganic elements with which it is supplied by air 

 and water. The former, though perhaps not an absolute, is & general 

 characteristic of the animal kingdom ; the latter, but for the exist- 

 ence of which animal life would be impossible, is certainly the 



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