GENETICS 167 



tunity of reciprocal differentiation, and these special comple- 

 ments are nearly always the result of symbiotic processes. 



For that which renders two important "characters" 

 " alternative " is specialisation for mutual work, and in this 

 light we can understand how the longer the process of mutual 

 specialisation has taken to perfect itself, the more readily will 

 the respective "characters" blend. We can thus understand 

 how two "good" "characters" may join forces to produce 

 physiological and general progress, i.e., symbiogenesis. We 

 can also understand how "characters " "previously independent 

 of each other " may sometimes under new conditions associate 

 in Xature or be artificially associated so long as at least some 

 degree of bio-economic compatibility exists. There is 

 generally at least some kind of racial and also of individual 

 " property," some capacity for service in each case. But when 

 accumulations of property have been reduced, when both 

 domestic and biological symbiosis are resting on the slenderest 

 foundations and service is becoming one-sided, or ceasing 

 altogether, a permanent or progressive union becomes impos- 

 sible. In all cases it is the qualitative and not the 

 chronological factor that determines the result, that determines 

 the degrees of physiological fertility or infertility. 



That frequently in spite of a threefold line of defence 

 digestion, fertilisation and segregation of "characters" patho- 

 logical transmission actually takes place, and the pathological 

 condition may persist for a long time, that " Mendelian " 

 factors appear so frequently associated with pathological 

 " characters," is further proof of the impossibility of dealing 

 adequately with the phenomena here concerned with a mere 

 chronological, or a mere quantitative and haphazard, instead 

 of a proper qualitative method. 



Dr. Walker also suggests that we have in certain con- 

 stituents of the cell the chromosomes and the mode in which 

 they are alternatively distributed to the gametes upon fertilisa- 

 tion, an exact parallel to the distribution of the characters in 

 Mendelian inheritance, which in my opinion, particularly in 



