424 THE BEGINNINGS OF LIFE. 



certain metabolic changes constituting the first steps 

 towards the production of new organisms. On the 

 other hand, the organic matter in the infusion exists 

 in a state of solution, and certain primordial living 

 units must appear in it, must aggregate and fuse, 

 before distinct masses of living matter can exist, in 

 which secondary metamorphic changes may take place 

 leading to the production of higher organisms. 

 Amongst such aggregates, also, it would seem likely 

 that more of uniformity would exist than in por- 

 tions of the actual tissue of a plant or of an animal 

 shortly after it had begun to die. The mere size or 

 bulk of the masses which are submitted to this simul- 

 taneous change has been shown, in both cases, to have 

 much influence over the kinds of organisms that are 

 produced. The higher forms are almost always evolved 

 from the larger masses, unless, from some unknown 

 cause, an accidental segmentation of the mass has 

 been initiated — though then, again, the same law is 

 exemplified, since, instead of one large and more or 

 less complex organism being produced, many small and 

 comparatively simple creatures are evolved. It would 

 seem that in the larger mass, made up as it is of living 

 matter of extreme instability, there is a wider field for, 

 as well as an increased liability to, the occurrence of 

 those successive molecular differentiations which must 

 occur in the production of higher organisms. 



There is still another cause, to which we have not yet 

 adverted, which doubtless strongly favours the occurrence 



