No. 543] BIOTYPES AND PHYLOGENY 



141 



in affirming that any one theory or hypothesis contains 

 all the truth. Thus we are coming to realize that neither 

 the Darwinian nor the De Vriesian theory of the nature 

 of the material upon which selection works is altogether 

 complete in itself and that neither when properly under- 

 stood wholly debars the other. If we accept the current 

 Mendelian and genoplast theories of heredity, must we 

 not admit that all variation is fundamentally discontin- 

 uous and that what has been called continuity is not 

 really such? It may be convenient to use such terms as 

 "continuity" and "discontinuity" but are they net suh 

 jective ideas rather than objective realities of impor- 

 tance? So, too, is it necessary to claim that the geno- 

 plast theory of heredity contains all the truth mid that 

 the transmission or "phenotype" theory is wholly false.' 

 It is easy to see how in pure line breeding " ancestral in- 

 fluence" is, as Johannsen says, "a mystical expression 

 for a fiction" but in the complicated polvgenoplastic 

 groups of the higher Metazoa it is hard to see why the 

 history of the formation of a gamete may not be of im- 

 portance. Is this not virtually admitted by Johannsen 

 when he grants the existence of " perturbations hy in- 

 fection or contamination"! And if this be granted, why 

 is there any necessary antagonism between the genoplast 

 theory of heredity and the belief that ' 1 discrete particles 

 of the chromosomes" may be "bearers of special parts 

 of the whole inheritance "? 



However this may be, none of us has any doubt that the 

 discovery of biotypes has been a real stimulus to experi-* 

 mental work, and there is no reason why it may not also 

 be a stimulus to the investigation of phylogenetic prob- 

 lems even though it does not assist greatly in their im- 

 mediate solution. Among the difficulties of the Bystem 

 atist perhaps none is better known than that which we 

 may call the problem of large genera— genera made up 



many of which are poorly defined and more or less inter 

 grading. Some of these genera, as Crataegus, Unto and 



