The likeness of offspring to their parents is extremely great and goes into many details; this we frequently overlook because a divergence strikes us more than a similarity. A similarity becomes striking when it is a question of familiar peculiarities. These often relate to exterior unimportant peculiarities. Our collection contains a pedigree (taken by Dr. Walter Bell from Bateson's "Mendel's Principles of Heredity"), Figure C 5, of a family with peculiarly curled hair; also in Figure C 6, a case of heredity of a lock of white hair, likewise taken from Bateson's work by Rizzoli.
The heredity of physical qualities is strikingly illustrated in Weinberg's Table C 7, showing the age at death of the parents and the marital gross and nett fertility. It is founded on the Stuttgart family registers, and comprises about 1,900 non-tubercular and about 3,000 tubercular families ("Archiv für Rassen and Gesellschafts Biologie" and Württemberger Jahrbücher für Statistik und Landeskunde, 1911). W. Weinberg adds:
Relation of Age at Death of Parents to Gross and Nett Fertility.
(After Weinberg.)
| - Non-tuberculous families, number of children surviving 20th year. | |
| - Tuberculous " " " " " | |
| - Non-tuberculous families, number of children dying before attaining 20th year. | |
| - Tuberculous " " " " " |
Number of non-tuberculous families about 1,900 (1876-79-86), of tuberculous about 3,000 (1873-89); from Stuttgart family registers.
Figure C 7.
"The gross as well as the nett fertility of those which have died increases with the age attained, the latter, however, in a greater degree, because the mortality of children decreases with the greater age attained at death. With the wife the curve is less steep and less regular, because in her case mortality is unfavourably influenced by the birth functions; this is particularly plainly seen in the case of tuberculous women, when the curve has two peaks."