EVOLUTIONS OF ORGANIZATION. 17 
warned him from adhesion to spontaneous gener- 
ation. But I hold him to be right in considering 
the progress from simpler to more complex life in 
the history of the earth as being analogous to the 
development of an individual from the embryonic 
to the adult condition, a definite, and not an inde- 
finite evolution. 
Such were the various views involving an evol- 
ution in one sense or another with which biology 
was familiar before the year 1859, when Darwin’s 
Origin of Species made its appearance. In that 
work there is full agreement with Lamarck in res- 
pect that the origin of life from a creator is frankly 
and continually referred to, and that the question 
brought up is essentially the old one of the degree 
in which forms through long epochs of time are 
capable of changing; but spontaneous generation 
is let alone, and the author is content to express 
his belief that “animals have descended from at 
most only four or five progenitors, and plants from 
an equal or lesser number.”* The new element 
imported into the discussion is, as you are aware, 
what he terms “natural selection,” a result of the 
struggle for existence. This struggle for existence 
had already been pointed out by Owen’ as a potent 
1 Origin of Species, 3rd edition, p. 518. 
? Zoological Transactions, voliv, p. 15. See, also, Comparative Anat- 
omy of Vertebrates, vol. iii, p. 799. 
