10 
relate it most usefully to other phenomena, but we still know no 
more of the particular phenomenon, than that under certain 
circumstances the apple does fall.” Even so it is with growth; we 
know exactly how the cell will behave, we can describe the steps 
of its progress, and we call this process growth, and rightly so too, 
as a comparative term, but all we really do know is, that under 
certain circumstances the cell grows ; and in spite of all that we 
have learnt, the grand problems which puzzled the wise man of eight 
and twenty hundred years ago, remain for us just as much unsolved 
as they were for him. We have learned, so to speak, all the 
mechanics of the process, but the wise men of our day can no more 
explain how that process comes about in the first instance, than 
Solomon himself could. 
If it be correct, as no doubt it is correct, that the primitive cells 
of animals and vegetables are so nearly alike that we cannot dis- 
tinguish between them, this surely is only a proof of our want of 
power to discern differences that we must certainly believe to exist ; 
for if we suppose one cell to be the parent cell of a highly organised 
animal, and another of an equally highly organised vegetable, it is 
clear that the two cells must be endued with totally different 
potentialities, the presence of which we fail to perceive, and not 
only with potentialities, of which we have heard a good deal, but 
also with necessities of development, of which, I think, we have 
heard too little. Each of these two cells not only can, but must, 
develop into a perfect individual of its own kind ; it has no choice, 
it cannot stop short at any particular stage and complete its life 
there, it must either attain its perfect growth, or become sterile 
and die. We know that in the process of growth highly organised 
animals, and plants also, pass through temporary stages which 
represent the perfect states of less highly organised families ; but 
we find that there is no power in the growing individual to arrest 
its growth and complete its life at any one of these stages, short 
of the ultimate one belonging to its own family, and if all the 
organisms which complete their growth at these different stages 
start from what are, to our comprehension, precisely similar cells, 
we must, I think, acknowledge the action of some inherent com- 
