SPOXTAXEOUS GENERATIOX AXD EVOLUTIOX : COXCLUSIOX 371 



and with it self-maintenance and multiplication ; and that would be 

 the first instance of selection ! 



But let us leave these imaginings, and wait to see whether the 

 chemists will not possibly be able to furnish us with a starting-point 

 for a more concrete picture of the first origin of life. In the meantime, 

 we must confess that we find ourselves confronted with deep darkness. 



The question as to the ' Where ' of spontaneous generation must 

 also be left without an}^ definite answer. Some have supposed that 

 life began in the depths of the sea, others on the shore, and others in 

 the air. But who is to divine this, when we cannot even name 

 theoretically the conditions and the materials out of which albuminoid- 

 like substances might be built up in the laboratory? Nageli's 

 hypothesis still seems to me to have the greatest probability. 

 According to his theory, the first living particles originated not in 

 a free mass of water, but in the reticulated superficial layer of a fine 

 porous substance (clay or sand), where the molecular forces of solid, 

 fluid, and gaseous bodies were able to co-operate. 



Only so much is certain, that wherever life may first have 

 arisen upon this earth, it can have done so only in the form of the 

 very simple and very minute vital units, which even now we only 

 infer to be parts of the living body, but which must first have arisen 

 as independent organisms, the ' BiophoridjB.' As these, according to 

 our theory, possessed the character of life, they must have possessed 

 above all the capacity of assimilating in the sense in which the 

 plants assimilate, that is, of renewing their bodily substance con- 

 tinually from inorganic substances, of growing, and of reproducing. 

 They need not on that account have possessed the chemical constitu- 

 tion of chlorophyll, although the capacity of assimilation in green 

 plants depends upon this substance, for we know colourless fungi, 

 which, notwithstanding the absence of chlorophyll, are able to build 

 up the substance of their body from compounds of carbon and nitrogen. 



The first advance to a higher stage of life must have been brought 

 about by multiplication, since accumulations of Biophoridas, un- 

 integrated but connected masses, would be formed. 



In this way the threshold of microscopical visibility would 

 gradually be reached and crossed, but — to argue from the modern 

 Baccilli — long before that time a differentiation of the biophors on 

 the principle of division of labour would have taken place within 

 a colony of Biophoridfe. This first step towards higher organization 

 must probably have taken enormous periods of time, for before any 

 differentiation could occur and bring any advantage the unintegrated 

 aggregates of Biophors must first have become orderly, and have 



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