ml CONCLUSION AND SUMMARY 155 



that relativity of magnitudes which constitutes form ; and so we 

 have studied it as a phenomenon which stands at the beginning 

 of a morphological, rather than at the end of a physiological 

 enquiry. Under these restrictions, we have treated it as far as 

 possible, or in such fashion as our present knowledge permits, on 

 strictly physical lines. 



In all its aspects, and not least in its relation to form, the 

 growth of organisms has many analogies, some close and some 

 perhaps more remote, among inanimate things. As the waves 

 grow when the winds strive with the other forces which govern 

 the movements of the surface of the sea, as the heap grows when 

 we pour corn out of a sack, as the crystal grows when from the 

 surrounding solution the proper molecules fall into their appro- 

 priate places : so in all these cases, very much as in the organism 

 itself, is growth accompanied by change of form, and by a develop- 

 ment of definite shapes and contours. And in these cases (as 

 in all other mechanical phenomena), we are led to equate our 

 various magnitudes with time, and so to recognise that growth is 

 essentially a question of rate, or of velocity. 



The differences of form, and changes of form, which are brought 

 about by varying rates (or "laws") of growth, are essentially the 

 same phenomenon whether they be, so to speak, episodes in the 

 life-history of the individual, or manifest themselves as the normal 

 and distinctive characteristics of what we call separate species of 

 the race. From one form, or ratio of magnitude, to another there 

 is but one straight and direct road of transformation, be the 

 journey taken fast or slow; and if the transformation take place 

 at all, it will in all hkelihood proceed in the self -same way, whether 

 it occur within the life-time of an individual or during the long 

 ancestral history of a race. No small part of what is known as 

 Wolff's or von Baer's law, that the individual organism tends to 

 pass through the phases characteristic of its ancestors, or that the 

 life-history of the individual tends to recapitulate the ancestral 

 history of its race, lies wrapped up in this simple account of the 

 relation between rate of growth and form. 



But enough of this discussion. Let us leave for a while the 

 subject of the growth of the organism, and attempt to study the 

 conformation, within and without, of the individual cell. 



