56 Transactions British Mycological Society. 



above we perceive the species to be both event and thing, an 

 event giving rise to a thing, a dynamic process resulting in a 

 static equiUbrium which is inherently stable. As the event, the 

 intimate process by which environment acts upon protoplasm 

 and hence upon gross form, is at present beyond our reach, we 

 must be content to accept the result, the thing, as a sort of 

 algebraical symbol for the unanalysed process which precedes 

 it and is its proximate cause. 



From these considerations we find ourselves led back to the 

 morphological basis of specific distinction and it may be useful 

 to reflect now, that the species is historically a morphological 

 idea and to protest against the unjustified transference of an 

 understood and accepted epithet to a hypothetical and possibly 

 non-existent unit. Whether the group of individuals be big or 

 little, diagnosed by a syndrome of characters or by a single one, 

 the term species is rightly applied to it if it remains visibly con- 

 stant under constant conditions. But, when we go beyond this to 

 seek for imagined immutabilities abstractable from such a group 

 by experimental analysis we pass to a region of new concepts 

 demanding the employment of new terminology. Where mor- 

 phological data are of the simplest order it is only natural that 

 physiological criteria should predominate in the discrimination 

 of groups; but no bacteriologist would pretend that types thus 

 delimited are fixed entities any more than the others. On the 

 other hand where morphological data are abundant they will 

 naturally influence the student most. To draw a hard and fast 

 line between the two procedures or to attempt to oppose them 

 to each other in distinct categories, as has been done, is logically 

 impossible. The student of higher groups knows, as a general 

 rule, little directly about their physiological make-up. He 

 has had to be content to rely upon their morphology as. 

 an eidolon of the inner mysteries; but where systematic bio- 

 chemistry has come to his aid it is gratifying to observe how 

 little it has found it necessary to amend the existing order; 

 a striking vindication of an implicit assumption, venerable from 

 age but none the less an assumption, that form is an index of 

 constitution, which has not perhaps been allowed its full 

 significance. 



The species is properly a four-dimensional concept whatever 

 the characters by which it is marked off. The time factor enters 

 into it either in consideration of its stability, on the one hand, 

 or as affecting, on the other hand, the sequence of events, deter- 

 mined by the impressionability of the organism in face of 

 varying environments, which provide the material the dynamic 

 phyleticist works with. Even were the organism a veritable 

 Proteus, every phase which achieves a static existence becomes 



