1891.] Are Acquired Variations Inherited ? 205 
direct evidence, since these structures pers not only the most in- 
teresting correlations and 
also the successive addition of new elements (qualitative variation). 
I believe the unanimous opinion of all those who have examined 
such series is that such variations follow definite lines from their 
incipient stages. This is a positive form of evidence, unless the 
observers are at fault, but cannot be considered as proof if it can 
be shown that these infinitesimal stages arise indefinitely, for if the 
advanced condition is useful the incipient condition must. possess 
some degree of utility, and would ex hypothesi be sélected. This 
objection is met, however, by the additional fact that the first ap- 
pearance of such structures is also not indefinite,—~. e., at definite 
adaptive points. In other words, the birth is as definite as the 
growth.” 
To sum up, the opinions of the two sides as to the nature of 
blastogenic variations are as follows: 
Both will admit.: 
I. That there are general fortuitous variations, which may be 
best explained as due to the spontaneous variability of the germ- 
cells, especially seen in their union. 
II. That there is also a class of variations, also springing from 
the germ-cells, which are in one sense definite, —?. e., in certain 
directions,—but not necessarily adaptive. 
One side denies, the other affirms : 
III. That there is also a large class of blastogenic variations 
which follow definite lines of adaptation. i 
What are the relations of these three classes of variations to 
+ me Y -d 
var iation), but 
ravronment ? 
. What are the Direct and Indirect Relations EER Environ- 
ment and Variability >—How far does ct the germ 
cells directly, and how far through changes in the somatic cells ? 
It is well known that a change of environment, especially to 
more favorable conditions, as in domestication, increases Varia- 
See cea the enormous mass of material available may be gained from the 
on that the teeth of all the Mammalia have sprung from a similar type 
allt aad aK dies ge. See the papers of Cope, Wortman, and the writer. 
