26 THOUGHTS ON NATURAL PHILOSOPHY. - 
heredity, and the differences of the power of the skin, etc., is 
that which allows of such great variation. But it is not only 
the power of the skin, there is also the question of the *size 
of the cells. The cells of some things are larger than the 
cells of others, and contain a larger quantity, if not a better 
quality, of nutrient matter; and consequently the daughter 
cells are larger, and as they increase and grow you get a 
larger object. There is more, however, than the mere 
question of size, there is likeness. Why an elephant and not 
a fish? The reply is that it is a question of the most delicate 
play of complex physical forces. Every reproductive cell, if 
it could be seen in its entirety, has its distinctive points and 
potentialities; and within and without are working forces 
that under similar conditions have only one result, limited in 
extent and +definite in end, so that with mathematical 
precision they produce effects that follow one another toa 
certain conclusion. Variation is caused by interference with 
those conditions or forces. : 
The question of sex, after its first evolution, appears to 
depend upon the virility of the parent cells. If the male 
reproductive celi is the more virile it will be the dominant 
factor and vice versa. When families are mixed in sex it 
results from the swing of the pendulum of virility between 
the reproductive cells. Physiologists know how many things 
go to produce virility, constitution, food, air, etc. 
A living cell is an electro-magnetic, and an electro-chemical 
machine, within an envelope, and living organisms of a 
higher type are electro-magnetic and_ electro-chemical 
“Physiologists would, perhaps more correctly, say that cells are 
generally nearly of the same size; but some are larger and some 
smaller; and that bulk is caused by increase of either. 
tDefinite in end in the sense that given certain conditions and 
forces certain results must follow. 
