172 THE BEGINNINGS OF LIFE. 



plex molecules of which it is composed are the results 

 of chemical combinations brought about by the same 

 physical agencies that suffice to engender other less 

 complex compounds from similar elements. And now 

 we have to follow up our studies concerning the nature 

 of the forms which this new-born living matter tends 

 to assume, and the modifications which the forms are 

 capable of undergoing we have, in fact, to build up that 

 portion of the subject which, if it applied to crystals 

 instead of organisms, would come under the head of 

 Crystallography. Having reference to living things, the 

 inquiry constitutes the empirical basis of Organic Mor- 

 phology. 



As we have already pointed out 1 , under the old 

 beliefs in c spontaneous generation,' there either were 

 or ought to have been included, two entirely distinct 

 processes. First, although less talked of than the other, 

 there was the process which we have called Archebiosis, 

 whereby living matter originates c spontaneously ; ' and 

 secondly, there were the processes of Heterogenesis, 

 whereby the matter of already existing living things 

 gives birth to other living units wholly different from 

 themselves, and having no tendency to assume or 

 revert to the parental type. It is this latter aspect, 

 therefore, of the old doctrines concerning c spontaneous 

 generation ' which we have now to consider. 



The belief in the fundamental unity of Life, under 

 every variety of organic form, is one of most ancient 

 1 Vol. i. pp. 244, 245. 



