THE DOCTRINE OF CONTAGIUM VIVUM. 315 



I see nothing unscientific, looking to the law of continuity 

 in the operations of nature, in the supposition, that it is 

 occurring at the present day somewhere or other on the 

 earth's surface, hut certainly not in decomposing liquids. 



Saprophytes are, as is well known, destitute of chloro- 

 phyll, and, like all such plants, they are unable to assimilate 

 carbonic acid. They obtain their carbon exclusively from 

 more complex compounds which have been prepared for 

 them by pre-existing living beings. It is, therefore, mani- 

 festly impossible that the primordial forms of life could have 

 belonged to this group ; for if we throw ourselves back in 

 imagination to that remote era when life first appeared on 

 the globe, we should find ourselves in a purely inorganic 

 world, amid conditions in which saprophytes could not 

 possibly live nor obtain nourishment. The special function 

 of saprophytes in the order of nature is to destroy, not to 

 create, organic matter ; and they constitute the last, not the 

 first, link in the biological chain. For if we regard the 

 order of life as it now proceeds on the earth's surface, we 

 may describe it as beginning with the chlorophyll body, and 

 ending with the saprophyte. The chlorophyll body is the 

 only known form of protoplasm which obtains all its nutri- 

 ment from inorganic sources ; here integration is at its maxi- 

 mum, and disintegration at its minimum, and the resultant 

 of the nutritive operations is increase of organic matter. 

 The saprophyte, on the contrary, feeds on nutriment pre- 

 pared for it by other beings ; here integration is at its mini- 

 mum, and disintegration at its maximum, and the resultant 

 of the nutritive process is decrease of organic matter. What 

 takes place in a decomposing liquid, under the action of 

 saprophytes, is progressive disintegration, and finally a break- 

 ing up of all the organic compounds it contains into carbonic 

 acid and ammonia ; and the process ends with the mutual 

 destruction of the organisms themselves. Organisms could 

 not, therefore, begin in this way. The primordial proto- 

 plasm must have been either the chlorophyll body itself, or a 

 body having a similar mode of nutrition. 



If the search for contemporary abiogenesis is to be con- 

 tinued, as doubtless it must be, for science is insatiable, it 

 appears to me that the inquirer should endeavour to realise 

 the conditions under which abiogenesis must have occurred 

 in the first instance. For, if the process be going on amongst 

 us at this day, it may be assumed as probable that it still 

 proceeds on the original lines laid down at the dawn of life. 

 If ever I should be privileged to witness an abiogenic birth, 

 I should certainly not expect to see a saprophyte ; I should 



