THE BEGINNINGS OF LIFE 



ment ; but in the present state of the question 

 they are entitled to serious attention. Dr. Bas- 

 tian argues, with great ingenuity, that just as 

 crystals, growing in a liquid menstruum, take 

 on shapes that are determined by the mutual 

 attractions and repulsions of their molecules, so 

 do these colloidal bodies, which we call monads 

 and bacteria, arising by " spontaneous genera- 

 tion " in liquid menstrua, take on forms that 

 are similarly determined. The analogy, how- 

 ever, is not exact. I am not disposed to deny 

 that the shape of a bacterium, or indeed of a 

 wasp, a fish, a dog, or a man, is due, quite as 

 much as the shape of a crystal of snow or quartz, 

 to the forces mutually exerted on each other by 

 its constituent molecules. But it must be re- 

 membered that in the case of an organism the 

 direction of these forces depends, in a way not 

 yet explained, upon the directions in which they 

 have been exerted by ancestral organisms. In 

 other words, a set of definite tendencies has been 

 acquired during the slow evolution of organic 

 life ; and it may well be doubted that, even in 

 the case of the bacterium, a tendency toward the 

 formation of single or double nuclei can have 

 been gained during the evolution of a single 

 generation of individuals. For in colloidal mat- 

 ter, as such, there is no definite tendency to- 

 ward the formation of nuclear spots, such as are 

 seen in bacteria. It is a main characteristic of 

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