HEKEDITY, AND THE OKIGIN OF SPECIES — MACDOUGAL. 507 



Vicinism, the somatic multiplication of bud sports and extreme 

 variants from a fluctuating series, and the confusion of closely related 

 elementary species form the basis for the greater number of mistaken 

 assertions as to the effects of cultivation. It is obviously necessary 

 to examine all facts bearing upon the lineage of supposedly new 

 forms, with the greatest care before their aspect, or behavior may be 

 taken as evidence upon phylogenetic problems. 



The theory of natural selection of an intraspecific application, as 

 one of which new forms might arise, is so well known that we need 

 not particularize in defining its ramifications. Briefly, it is assumed 

 that, as the whole mass of individuals comprised in a species is in a 

 constant state of variation, the individuals wdiich show features even 

 the most slightly better adapted to the environment survive, while 

 the less fit perish. Thus hj infinitely small changes during each 

 generation a species moves away from the ancestral type in one or 

 more directions until in the course of thousands of years the differ- 

 ences become so great as to be appreciable, and of a specific character, 

 to use an arbitrary phrase. Three insurmountable objections to the 

 acceptance of this method as universal present themselves. First, the 

 fluctuations exhibited by the individuals comprised in a species do 

 not in any known instance transgress definite measurable limits, and 

 do not depart from an ascertainable norm or average; secondly, the 

 gradual transition of individuals from one type to another, that is, 

 intergrading forms, demanded by this theory, are not found among 

 plants; and, thirdly, although we have preserved specimens and 

 records of several species which cover their history for many thou- 

 sands of years, yet such gradual transformations are not observable. 

 Lastly, it is to be said that it is extremely doubtful if the earth is 

 old enough to have permitted the development of the great number of 

 organisms which inhabit it b}^ this method. 



A secondary idea that has been formulated in connection with this 

 subject is that of orthogenesis, by which the organism evolves rudi- 

 mentary structures purely as a result of internal forces, and initially 

 without reference to utility or to environment. These rudimentary 

 organs may, in the course of generations, wax in size, undergo increas- 

 ing differentiation of structure, perhaps finally becoming subfunc- 

 tional, or even fully functional, although nascent organs are not 

 always supposed to attain this useful end. In support of this theory 

 it has been pointed out that plants and animals show many structures 

 which, so far as our understanding of them goes, are wholly without 

 part in the life of the organism. The present development of plant 

 morphology, however, is one which is carrying us farther and farther 

 away from the conception of such prefunctional formation of organs, 

 as the whole tendency of modern investigation is to place the morpho- 

 genic processes upon a physiological basis. On the other hand, the 



