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(2) Variation due to disturbance of the economy of the 
individual, in consequence of sudden changes of 
environment. Such changes may be considered as 
favourable,* and as unfavourable; and the un- 
favourable changes may be divided into those - 
oveasioned by disease, and those brought about by 
injury and mutilation. 
Il.—Normal or developmental Variation, that is, gradual 
functional modifications induced in the individual by the 
necessities of its environment. 
The ontogenetic changes by which an organism reaches 
maturity, or even later, are really developmental Variations 
inherited from the parent; the further ontogenetic changes, by 
which an organism responds to its environment are, strictly, 
developmental variations proper to the organism.t 
To a great extent the difference in the lines of thought 
adopted by Darwin and Spencer in regard to the origin of 
species, is that the former lays the greater stress on Abnormal, 
or as he calls it, Spontaneous Variation having suddenly 
produced some feature which gave its possessors superiority in 
the struggle for existence; while the latter regards Normal 
Variation (use and disuse) as the important factor. I shall 
have something to say on this point presently. 
Tae Law or Haruier INHERITANCE. 
I have said that it may be assumed “like produces like so 
far as the conditions of environment will allow;” but this 
does not meet the facts of the case, because the offspring only 
becomes like its adult parent by continual growth and change. 
Therefore it might be said: “the offspring at its various stages 
of life tends to assume what was the parental form at these 
* The luxuriant growth of wheat when top-dressed with nitrate of soda— 
the broader leaves and the darker colour. 
[ t Ontogenetic changes refer to the individual’s stages in relation to each 
other ; developmental variations refer to them in their relation to the parent] 
at i il ell at eal) or a ateg a . 
