BIOTYPES AND PHYLOGENY 



Dr. HUBERT LYMAN CLARK 



Museum of Comparative Zoology, Cambridge, Mass. 



[The substance of this paper was presented to the 

 American Society of Naturalists at the Princeton meet- 

 ing under the title "Pure Lines and Phytogeny.' ' Dr. 

 Johannsen entered an emphatic protest against the use 

 of "pure line" in the sense of a group of individuals 

 characterized by an identical combination of the same 

 determinants. Subsequent conversation with Dr. Jo- 

 hannsen, and the recent clear exposition by Shull {Sci- 

 ence, Jan. 5, 1912, pp. 27-29) satisfied me that what I had 

 considered "pure lines" (such as those distinguished by 

 Jennings in Paramcecium) are the pure strains called 

 biotypes by Johannsen. I have modified my paper ac- 

 cordingly and have avoided using the term "pure line." 

 I have also abandoned the very convenient term "pheno- 

 type" because my use of it as a contrast to biotype is 

 not strictly in accord with Johannsen's usage of it as a 

 contrast to "genotype." At Princeton, I protested 

 against Johannsen's use of the word genotype, because 

 the word is preempted for a totally different usage. 

 I suggested a substitute, but this failed to meet 

 with Dr. Johannsen's approval. Since I have seen 

 Shull 's definition of "genotype" (to which Dr. Johann- 

 sen himself referred me), I think the objection to the 

 word is greater than before because "type" implies a 

 single definite thing or model and Johannsen's "gen- 

 otype" is not that but is "the fundamental hereditary 

 . . . combination of genes of an organism." In other 

 words it is not a concrete thing but the intangible char- 

 acter of that thing. It seems to me the termination 

 "plast" (irWnfe, moulded, formed, i. e., formed from 

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