336 SYMBIOGENESIS 



as much as in the individual " characters" and powers of the 

 organism itself ; that is to say, that some of the factors making 

 for such inheritance are in the symbiotic environment and 

 cannot operate unless the symbiotic co-operation is fully 

 carried out, even though some of the factors, and perhaps the 

 most prominent, may be found in the organism itself. Such 

 co-operation is parallel to that of the sexes in simple 

 reproduction. 



If the main method of evolution symbiogenesis as sup- 

 ported by cross-feeding has so long escaped the ken of our 

 naturalists, we cannot be surprised to find that similarly the 

 manner in which essential acquisitions come and go, and meet 

 with biological approval or otherwise, has escaped them, or 

 only been occasionally glimpsed or partially realised. It is 

 always of prime importance in evolution to acquire useful 

 biological correspondences and to transmit only that w r hich is 

 in accordance with desirable adaptation. Other acquisitions 

 are but secondary, and, as we have seen, frequently of a 

 pathogenetic order. The latter, naturally enough, involve 

 endless conflicts in which, as we have seen, digestive, genetic, 

 and symbiogenetic momenta are primarily concerned. 



Acquisitions related to a pathogenetic order, therefore, are 

 fought against by Mature so long as possible ; but it does not 

 follow that the inheritance of all acquired characters is there- 

 fore abhorred, or that all "acquired" characters are non- 

 inheritable. It only follows that "characters" are heritable 

 in different degrees, according to the compatibilities and possi- 

 bilities of response in each case. 



Acquisitions of the normal order are inherited in due time, 

 and if their effects eventually become manifest as though 

 variation in a particular species proceeded by an orthogenetic 

 principle, this is because all normal and desirable acquisitions 

 are in accordance with a grand progressive bio-economic 

 principle, viz., with symbiogenesis, i.e., because they have met 

 with genuine biological approval. 



