98 ON THE LATEST FORM OF THE DEVELOPMENT THEORY. 
universal experience, in the case of well recognized and perfectly distinct species, that 
fertile offspring, capable. of continuing their own race, should be specifically different 
from their parents. Accordingly, if a new form or species appears, it cannot have been 
produced by ordinary generation, but must have been specially created. 
The other theory, resting mainly upon obscure and anomalous cases, or upon pro- 
cesses supposed to be of so great length that man cannot have witnessed the beginning 
and end of them, assumes that various species have been developed out of one another 
by ordinary descent, the progeny appearing, either immediately or after many genera- 
tions, specifically different from their parents or ancestors. According to this view, 
the multiplication of species takes place by a process perfectly analogous to that of the 
multiplication of individuals of the same species, though it is more infrequent or re- 
quires a greater length of time for its completion. This is the Development Theory, 
so called, which has been maintained, with various modifications, by Maillet, in a work 
called the * Telliamed,” by the French naturalist, Lamarck, by the English author of 
the “ Vestiges of Creation," and in its latest form by Mr. Charles Darwin. The earlier 
forms of it have been rejected by the wellnigh unanimous verdict of the scientific 
world; the latest has been urged with so much ability and candor, and has already 
found so many adherents, that it merits distinct and respectful consideration. 
Mr. Darwin's theory of the origin of species by development really consists of five | 
distinct steps or processes, which need to be sharply distinguished from each other, 
though two or more of them are often confounded under the same name. 
1. Individual Variation. — It is a well-known fact, that individual plants and animals 
are occasionally found to vary by slight peculiarities from the general type of the race 
or breed to which they belong. ‘The offspring is made a little bigger or a little smaller 
than its parent; or some organ, member, or limb is abnormally repeated or deficient, 
or wrongly placed, or unusually developed whether by excess or defect. 
2. Inherited Variation. — Generally, these abnormal traits are found only in the indi- 
viduals in which they first appear, the offspring of these reverting immediately to the 
ancestral or common type. Sometimes, they are continued by descent through two or 
three generations, and then finally disappear. Less frequently, if at all, they are con- 
tinued by inheritance indefinitely, so as to become the distinguishing mark of a peculiar 
breed. Mr. Darwin’s theory rests exclusively upon those which are thus perpetuated 
by inheritance; *any variation," he says, * which is not inherited is unimportant 
for us." S 
..9. Cumulative Variation. — One peculiarity having been perpetuated by inheritance, 
it is assumed that another may be superinduced upon it by a perfectly analogous 
