35 
which every such organism passes from its initial structureless 
germ to its complete development. It is the same law in the 
vegetable and the animal, in the apple-tree and the elephant, 
in the sparrow and the human body. It does not in the least 
account for the differences between these existences, or give 
any explanation of them, much less is it a cause , in any proper 
sense of the word, of their being what they are. It only 
affirms that the operation of the different causes, to which the 
development of the organism is due, must follow a certain 
order. The causes themselves, if we consider the case of an 
individual existence, are obviously twofold. 
First , the antecedent life, or lives, of which its own life is 
the continuity. 
Secondly , in a subordinate and very limited degree, the envi- 
ronments or conditions of the organism during its development. 
The first of these is undoubtedly in all cases the dominant 
cause. It is not only contrary to all experience that the 
derived existence should not be identical in kind with its 
antecedent or antecedents, but it would be inconsistent with 
the principle of continuity. But for this cause to produce its 
effect, certain environments or conditions are essential to the 
normal development. The absence of these, or any defect, or 
even excess in them, may render the development imperfect or 
abnormal, or even prevent it altogether. The limits of the 
effects that can be produced on the development of an indi- 
vidual organism by the alteration of its environments is a 
subject on which little is known with accuracy ; indeed, these 
effects are generally so small,* that it is only by observing the 
accumulation of the effects, after many successive generations, 
that any approximation can be made to a scientific treatment 
of the subject. This, as is well known, has an important 
bearing on a much larger question than that of the consecu- 
tive order of the cyclical changes of an individual existence : 
viz., whether it is possible that, through the accumulated 
effects of environments, there may have been an evolution 
of the different types of organic life somewhat analogous 
to that of the different stages of development in the in- 
dividual. This generalization assumes that, besides the law 
of continuity, which determines that each succeeding genera- 
* The instance that at first sight seems the most startling is that which 
is afforded in the natural history of bees, — of the queen bee being developed 
by additional food and heat (especially the former) from the larva of a 
working bee. But as the working bee is an undeveloped female, this is 
merely the case of a complete normal development requiring a certain amount 
of food and heat. There is a similar instance, I am informed, in the natural 
history of the termites , or white ants. 
D 2 
