634 THE BEGINNINGS OF IIFE. 



collocation which have been assumed by the molecules 

 of iron. 



Living matter is especially characterized by the com- 

 plexity of its molecules and their state of continual 

 intestine movement. This peculiarity, as well as other 

 related qualities, make the simplest aggregates of such 

 matter especially prone to undergo those secondary 

 structural rearrangements which all plastic and homo- 

 geneous masses of matter are liable to exhibit. And 

 although in the case of living matter, these re-arrange- 

 ments manifest themselves by producing what we call 

 ^organization,' still the forms and structures which 

 many of the lowest organisms tend to assume are 

 entirely referrible to the polarities of their molecules — 

 just as the forms of crystals are the results of similar, 

 though simpler, polarities. 



And, speaking generally, the complexity of 'organi- 

 zation •* attainable by the lower animal forms gradually 

 tends to increase as the masses of matter from which 

 new forms are to arise increase in size — owing appa- 

 rently to the multiplication of effects that may be 

 induced by the production of several series of molecular 

 rearrangements within the larger aggregates. These 

 rearrangements (developmental changes) often take 

 place rapidly and without appreciable increase in bulk 

 of the mass which undergoes them ; and the dissimilar 

 changes which may be seen to take place in different 

 masses are attributable to the existence of different 

 initial states of molecular composition. The changes 



