126 THE BEGINNINGS OF LIFE. 



the forms which minute specks of living matter tend 

 to assume; just as the study of crystallography has 

 taught us much concerning the limits of variation 

 observable in crystalline forms. 



The facts which are known concerning organic 

 development in general, and embryology in particular 

 revealing, as they do, the before-mentioned progress 

 from a minute homogeneous germ to the greater and 

 greater complexity of structure peculiar to the various 

 forms of life are so many indubitable evidences of the 

 tendency to develop which exists in living matter. As 

 Mr. Spencer says 1 : c Each organism exhibits, within a 

 short space of time, a series of changes which, when 

 supposed to occupy a period indefinitely great, and to 

 go on in various ways instead of one way, give us 

 a tolerably clear conception of organic evolution in 

 general/ Nay, more, in the development of the indi- 

 vidual we have a condensed embodiment of the modi- 

 fications which have slowly appeared in one or other of 

 the various representatives of an innumerable series of 

 more and more specialized ancestors. 



All Evolutionists, therefore, might be presumed to 

 believe that the persistent intrinsic mutability of 

 living matter, subject as it is to the constant incidence 

 of ever-varying physical forces, would cause it to 

 manifest a continuous tendency to undergo a further 

 differentiation of structure 2 . Whilst all our knowledge 



1 ' Principles of Biology,' vol. i. p. 349; 



2 For as Mr. Spencer points out (' First Principles,' 2nd ed. p. 548) : 



