THE UNITY OF NATURE. 263 



compounds of carbon — are the sole and the mechanical 

 causes of the specific phenomena of movement, which 

 distinguish organic from inorganic substances, and 

 which are called life, in the usual sense of the word " 

 (see The Natural History of Creation). Although this 

 " carbon -theory " is warmly disputed in some quarters, 

 no better monistic theory has yet appeared to replace 

 it, We have now a much better and more thorough 

 knowledge of the physiological relations of cell-life, 

 and of the chemistry and physics of the living proto- 

 plasm, than we had thirty- three years ago, and so it 

 is possible to make a more confident and effective 

 defence of the carbon-theory. 



The old idea of spontaneous generation is now 

 taken in many different senses. It is owing to this 

 indistinctness of the idea, and its application to so 

 many different hypotheses, that the problem is one of 

 the most contentious and confused in the science of 

 the day. I restrict the idea of spontaneous genera- 

 tion — also called abiogenesis or archigony — to the 

 first development of living protoplasm out of inorganic 

 carbonates, and distinguish two phases in this " begin- 

 ning of biogenesis ": (1) autogony, or the rise of the 

 simplest protoplasmic substances in a formative fluid, 

 and (2) plasmogony, the differentiation of individual 

 primitive organisms out of these protoplasmic com- 

 pounds, in the form of monera. I have treated this 

 important, though difficult, problem so exhaustively 

 in the fifteenth chapter of my Natural History of 

 Creation that I may content myself here with 

 referring to it. There is also a very searching and 

 severely scientific inquiry into it in my General 

 Morphology (1866). Naegeli has also treated the 

 hypothesis in quite the same sense in his mechanico- 



