114 GENETICS 



Organisms belong to the same phenotype with 

 respect to any character when their somatoplasms 

 are alike. They belong to the same genotype when 

 their germplasms are alike. 



The word "genotype" was suggested by Johanssen 

 in honor of Darwin and his theory of psmgenesis, 

 although there are certain objections to its use in 

 this connection for the reason that systematists have 

 already appropriated it in a different sense. 



Natural history and common usage deal prin- 

 cipally with phenotypes, that is, with organisms as 

 they appear. The older theories of heredity were 

 likewise concerned wdth phenotypes, but we are now 

 coming to see more clearly than before that heredity 

 must always be a case of similarity in origin, that is, 

 in germinal composition, and that similarity in ap- 

 pearance by no means always indicates similarity 

 in origin or true relationship. 



The assumption that similarity in appearance does 

 indicate relationship has been made the foundation 

 of many conclusions in comparative anatomy and 

 phylogeny, but to the modern student of genetics 

 who places his faith in things as they are, rather than 

 in things as they seem to be, conclusions based upon 

 phenotypical distinctions alone have in them a large 

 source of error which must be taken into account. 



In a museum of heredity, should such a collection 

 ever be assembled, the specimens would not be ar- 

 ranged phenotypically as they are in an ordinary 

 museum where things that look alike are placed 

 together as if in bonds of relationship, but they 



