HEREDITY, AND THE ORIGIN OF SPECIES. 5 
the effects of cultivation. It is obviously necessary to ex- 
amine all facts bearing upon the lineage of supposedly new 
forms, with the greatest care before their aspect, or beha- 
vior may be taken as evidence upon phylogenetic problems. 
The theory of natural selection of an intra-specific ap- 
plication, as one of which new forms might arise, is so well 
known that we need not particularize in defining its rami- 
fications. Briefly, it is assumed that as the whole mass of 
individuals comprised in a species is in a constant state of 
variation the individuals which show features even the 
most slightly better adapted to the environment, survive 
while the less fit perish. Thus by infinitely small changes 
during each generation a species moves away from the an- 
cestral type in one or more directions until in the course of 
thousands of years the differences become so great as to 
be appreciable, and of a specific character, to use an arbi- 
trary phrase. Three unsurmountable objections to the ac- 
ceptance of this method as universal present themselves. 
First, the fluctuations exhibited by the individuals com- 
prised in a species do not in any known instance transgress 
definite measurable limits, and do not depart from an as- 
certainable norm or average. Secondly, the gradual tran- 
sition of individuals from one type to another, that is inter- 
grading 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 thousands 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, by this method. 
__ A secondary idea that has been formulated in connec- 
tion with this subject is that of orthogenesis, by which the 
organism evolves rudimentary structures purely as a result 
of internal forces, and initially without reference to util- 
