THE PHENOMENA OF LIFE 149 



reaction to internal impressions, immediate or deterred, be 

 considered as the characteristic of life, since osmotic growths 

 exhibit a most exquisite sensibility in this direction. Since, 

 then, the faculty of reaction is a general property of matter, 

 the characteristics of life in the lower organisms are only three 

 in number, viz. nutrition, growth, and reproduction by fission 

 or budding. Hut crystals are also nourished and grow in the 

 water of crystallization. They have moreover a specific form, 

 and every biologist who wishes to establish a parallel between 

 the phenomena of the living and the mineral world is wont to 

 compare living beings with crystals. Crystals, it is said, affect 

 regular geometric forms, salient angles, and rectilinear edges, 

 while living beings have rounded forms without any geometric 

 regularity. Another supposed distinction is that living beings 

 are nourished by intussusception, whereas crystals increase by 

 apposition. Again, living beings are said to assimilate and 

 transform the aliment they absorb, whereas crystals do not 

 transform the matter which is added externally to their 

 structure. Another supposed difference is that living things 

 eliminate and discharge their products of combustion, while 

 the evolution of a crystal is accompanied by no such elimina- 

 tion. Finally, the phenomenon of reproduction is said to be 

 the exclusive characteristic of a living being ; but crystals may 

 also be reproduced and multiplied by the introduction of 

 fragments of crystalline matter into a supersaturated solution. 



The resemblance between an osmotic growth and a living- 

 organism is much closer than that between a living being and 

 a crystal, there being not only an analogy of form, but also of 

 structure and of function. In order to find the physical 

 parallel to life, we must turn to osmosis and osmotic growth 

 rather than to crystals and crystallization. 



The first and most striking analogy between living beings 

 and osmotic growths is that of form. The morphogenic 

 pow- 



er of osmosis gives rise to an infinite variety of forms. 



6 



An osmotic growth, even at the first sight, suggests the idea 

 of a living thing. ( hie need only glance at the photographs 

 of osmotic productions to recognize the forms of madrepore, 

 fungus, alga, and shell. It is wonderful that a force capable 



