176 THE MENDEL JOURNAL 



men appear to group themselves into groups ? 

 Assume that it may appear to be the case, is it 

 really so ? May not a whole group of qualities — 

 inherited as a whole — be simply due to some simple 

 hereditary factor, such as the Nissl granules, or to a 

 few factors hereditarily coupled together ? When 

 such a contention as that maintained by my opponent 

 is accepted by her, is she not merely making an 

 assumption ? She is assuming that appearances are 

 realities. If we must make assumptions at all, at 

 least let us do so in accord with our available 

 knowledge, and not in discord with it. 



There is yet more to be said against her con- 

 tention. Physiological knowledge leads us to the 

 conclusion that our spontaneous and reflex actions 

 depend upon the existence of certain groups of 

 nerve cells, collectively spoken of as nerve centres, 

 which may act either singly or in combination with 

 others. The nerve centre that controls the beating 

 of the heart is lodged in a certain area of the 

 hind-brain ; that of speech, which appears to be 

 asymmetrical, in another area ; that of audition in 

 another, and so on. Now, in the course of individual 

 developement, whence came these groups of cells ? 

 Eecent embryological investigations of the experi- 

 mental order show us clearly that, not only groups 

 of cells, but whole organs, may take their origin 

 from a single cell or blastomere, in the early stages 

 of the segmenting embryo. If that cell is destroyed 

 the organ which arises from it will be absent in the 

 definitive (adult) stage. Such a cell may be regarded 



