868 



coupling of the factors. In both cases one obtains then from pairing 

 of exteriorly the same individuals {Aa Bb's among each 'other) 

 different groups of descendants. Baur found with races of Antir- 

 rhinum in the first case coupling, in the second case common segregation. 



It is quite possible, that in the motion of heredity of the shape 

 of the head, coupling of factors for the length and the width occurs. 

 This means consequently, that in general the shape of the head can 

 be conceived as one single seiies of mendelian properties (because 

 the factors for the length and the width have coupled) but that in 

 some cases deviations will be found, which are the consequence of 

 the meeting of gametes of the very rare not coupled factors of the 

 length and the width. We shall take account of this consideration 

 for the further examination of the tables. 



Table I and II contain examples of families a single member 

 of whom possesses a strongly deviating headform. This deviating 

 headform is nearly always brachycephalic (the single time (fam. 

 XVI), that the deviation is dolichocephalic, only one of the 

 parents is known ; the great lengths of the heads of the other 

 members of the family render it very likely that the unknown father 

 has also had a large head) and this brachycephaly always relates 

 to a short head; in one case (CLXIV) this is not so; yet there 

 the width of the head neither surpasses that of the other members 

 of the family, and the length (18.3) is considerably less than that 

 of the others (18.7 — 19.7). More exact than to say that in the 

 families of table II one single brachycephalic headform appears, 

 which points to recessivity of brachycephaly, it is to distinguish hereby, 

 that in these cases (table 1), the brachycephaly is restricted to a 

 very short head, and that the shorter head is recessive with regard 

 to the large one. 



At the occurrence of separate deviations one must also think of 

 accidental causes. One may have to do with a not-inheritable varia- 

 tion, consequently a modification. Exterior circumstances, illness or 

 trauma, can likewise be rhe cause of a deviation. With an entirely 

 unexpected result one will have to think of the great experimental 

 mistake by the analogon of what is called in plants vicinism. For 

 the persons of table I the first cause cannot directly be traced, as 

 they are still young or not further known. With regard to the 

 second cause of family 164 d^ with the deviating index 83.5 and 

 short, small head, we remark, that it is a backvvard girl, who suf- 

 fered much from illness in the first years of her life, and has been 

 nursed during a long time in the children's hospital on account 

 ^f weak condition of the osseous system. Only very late the child 



