92 Proceedings of Royal Society of Edinburgh. [sess. 
offspring and parent, both in general and in particular, alike in 
normal and in pathological characteristics, cannot be denied as a 
fact, it has often been denied as the result of transmission. Such 
denials have varied greatly in degree and motive, and some of the 
most important may thus be classified. 
1. Denial of any transmission, on philosophical grounds; e.g ., 
Wollaston. 
2. Denial of the transmission of individual characteristics ; e.g., 
Bonnet. 
3. Denial of the transmission of psychical individual character- 
istics; e.g., Buckle. 
4. Denial of the transmission of characters individually acquired 
by the “body” of the parent in course of function, or impressed 
upon the same by the environment ; His and others, but notably 
Weismann. 
Of those denials the only one of serious importance is that of 
Weismann, which will be separately considered later on. The 
truth which the others more or less clearly suggest is the influence 
of similar conditions of function and environment in evolving 
resemblances, without there being any real transmission of the 
same. This all naturalists will allow, while at the same time 
refusing to believe that similar conditions are sufficient to account 
for the greater part of the result. Of coarse, if we push back far 
enough and include in the similar conditions the specific constants 
in the history of the germ-cells, in the mechanics of development* 
and in the life of the embryo, the denial becomes more reasonable* 
though more truistic. 
II. Problems of Heredity. 
There are three general problems of heredity, which must be 
carefully distinguished, as has not always been done. 
1. In what consists the unique character of the germ-cells? 
2. Granted the unique character of the germ, what are the con- 
ditions of its reconstruction of the parent ? 
3. In what way is the reappearance of individual peculiarities, as 
opposed to that of the general features, to be interpreted ? 
In other words (1) it is necessary to understand in what way the 
germ-cell of plant or animal comes to be such a marvellous unit 
