871 



children have likewise a short and small head. So of fam. 36 three 

 children are short-headed, of fam. 73, of fam. 234 and of fam. 87c 

 likewise; of fam. 16c four children are short-headed. When |)ernsing 

 the tables, which will be published later, we are struck by the 

 same fact. This occurrence in groups of the short, small head points 

 to its independent signification for heredity. There must be a 

 special reason for its appearance: we have to do with a new se- 

 gregation. As in the different breeds of mice of Cüénot, Durham and 

 others the crossing of the gray mouse with the albino-mouse gives 

 besides gray and albino mice likewise black ones, so here also at 

 the crossing of two shapes of heads a third type appears among 

 the children. This phenomenon of the concealed existence of a 

 factor, revealing itself only at a special crossing is called by Bateson 

 epistasy. We can admit that for the formation of the short, small 

 head the meeting of two factors is necessary; if the large and wide 

 head possesses one of these factors, then by crossing this factor can 

 combine itself with the other factor for the small head and produce 

 this headform. The crossing 124 is likewise interesting for 

 this conception, the mother has a short and small head and a high 

 index (86.9), the father is brachycephalic (82.2) has a not large 

 head, all six children of this family have short and small heads with 

 high indices (81, 85, 86.5, 87.5, 88, 86.5). This case is anologous 

 with the crossing albino X black = all black. 



I am not of opinion that my material can already prove the 

 conception given here, but it is already of importance that we can 

 bring back a conspicuous phenomenon to a thoroughly investigated 

 form of segregation. 



The sex exercises certainly likewise its influence on the shape 

 of the head. This appears already from the curves (Fig. 2, 3 and 

 6. The complete material indicates also distinctly that the 

 heads of women are smaller than those of men. When perusing 

 the tables we are struck by the fact how seldom the large head of 

 the mother returns among the children. Consequently special con- 

 ditions must be satisfied too, if the large headform is found in 

 woman; there is a preference for the small, short head in woman. 

 I remind here of the investigations of Pearl, Morgan and others 

 into heredity restricted to sex (correlation of sex), but I defer the 

 examination of the material with regard to this phenomenon to a future 

 time, when I can dispose of a more extensive material. 



When testing our material to the Mendelian experience we must 

 take into consideration some more complications. So we know an 

 intensifying and a weakening factor, likewise a transformation-factor. 



