308 The Unity of the Organism 



Revised Conception of Heredity Essential to Interpreting 



This Interdependence 



On the basis of the objective evidence what is the prob- 

 able meaning of the interdependence between attributes of 

 full-grown organisms and chromosomes of the germ-cells? 

 There is the utmost diversity of view as to what heredity is 

 and as to what facts come under it. It seems almost as 

 though the more the subject is investigated the more diverse 

 the views become. This I think is literally true for the 

 theoretical side of the subject, though it is certainly not 

 true with reference to the factual side. The discovery by 

 Mendel of the principle of segregation of cliaracters while 

 they are still latent in the germ-cells, and the elaboration 

 of this principle by later investigators, is a positive achieve- 

 ment of high rank, destined to stand for all time. And sucli 

 negative results as those of the disproof of telegeny, of the 

 influence of "maternal impressions," and of the inheritance 

 of acquired characters in the old pre-Weismannian sense, 

 must be counted as factual achievements of much practical 

 importance. 



Unwarrantable Tendency to Restrict Heredity to Sexual 



Propagation 



Heredity as used in biology has to do with the reproduc- 

 tion of plants and animals. That the growth of an oak 

 tree from an acorn and of a rooster from a hen's egg illus- 

 trate heredity there can be no doubt. These typify a great 

 number of cases, all those in which the plant or animal de- 

 velops from a germ-cell, an exceedingly minute, simple body 

 as compared with the full grown organism. But what about 

 reproduction through other means than such cells .^ Is 

 there heredity in propagation by other means .^ Much of 

 the recent discussion of the subject is practically restricted 

 to heredity among germ-producing organisms ; and some 

 of the foremost writers on the subject are explicit on this 



