140 THE BEGINNINGS OF LIFE. 



is incomplete the dissepimented parts have a tendency 

 to grow in unison, so that an actual increase in siz,e 

 of the several parts and of the whole organism takes 

 place. But where the segmentation is complete and 

 rapid, no increase in bulk of the respective units is 

 able to occur. 



As growth progresses it is almost invariably found, 

 on examination with high microscopic powers, that the 

 'Bacteria^ which at first appear to have a homogeneous 

 consistence, gradually acquire a hollow character. They 

 seem to undergo the first differentiation, which results 

 in the separation of an outer and more consistent layer 

 from an internal and more fluid contents. The same 

 kind of thing is visible in Vibriones and Leptothrix fila- 

 ments though in them, and also in Fungus-mycelium 

 of different kinds, the extent to which this differentiation 

 is perceptible is very various. Some specimens of each 

 of these filaments seem more or less semi-solid through- 

 out, and present no distinct bounding wall whilst in 

 others the bounding wall is most apparent, and no 

 solid contents are recognizable. The size of the seg- 

 ments, or the frequency with which dissepiments occur, 

 is as variable in Vibriones and Leptothrix as in mycelial 

 filaments. 



We see in some Vilriones and Leptothrix filaments 

 that the segments are short and deeply divided, so as 

 to produce necklace-like chains, each unit of which 

 more closely resembles the 7V#/*-corpuscle than a 

 Bacterium. 



