58 Causes and Course of Organic Evolution 



The spores and even the active cells of some bacteria resist 

 drying dessication for not merely months, but also it may be 

 for years. 



In their action alike on crystalloid and on colloid bodies — 

 inorganic and organic — the bacteria show themselves to be 

 minute but highly complex colloid mixtures, which, in virtue 

 of their o^^Tl definite chemical structure, act on definite chemi- 

 cal bodies, so as to change their composition. In the process, 

 food materials and supplies of energy are thus secured by the 

 bacteria, which then utilize these supplies for their own growth 

 and multiplication. 



The rapidity -^ith which they undergo division at one stage, 

 and spore formation at another stage of their history, is often 

 amazing, and recalls in final results the rapid formation of 

 chemical products on an extensive scale. Thus it has been 

 calculated that, since the cholera organism divides its cell in 

 20 minutes, were food supplies and other needed environal 

 conditions suitable, it would have produced 16 hundred trillions 

 of cells in a day, and the resulting mass would represent 100 

 tons of solid residue (39: 17). 



The dehcate wall of each cell individual consists in part of 

 cellulose, or, as in the zoogloea stage, of a mucilaginous modi- 

 fication of this in which the cells are embedded, exactly as in 

 many Schizophycese. But most are agreed that the cell-wall 

 of the higher bacteria consists largely of a nitrogenous sub- 

 stance — probably albuminous — as is observed in animal walls. 

 So here, as in most details of structure, the present group may 

 well have included forms from which a few of the higher plant 

 types started, and equally the primitive types of animal. 



While the simple spherical or coccoid bacteria are devoid 

 of cilia, many of the rod forms have one to many cilia. These 

 may vary from a single terminal whip to a terminal bunch 

 and again to diffusely ciliate examples. Such organisms can 

 move with extreme rapidity in their appropriate liquid media, 

 and recall vividly types like Herpetomonas and various Coccidia 

 amongst the unicellular animals. 



On the whole it may be said that, while the simpler Schizo- 

 mycetes and the Schizophyceae have gradually elaborated a 



