This is the only case known to me of a new stage in the development of a Number-Form being suddenly attained.
DESCRIPTION OF PLATE III.
Plate III. is intended to exhibit some instances of heredity. I have no less than twenty-two families in which this curious tendency is hereditary, and there may be many more of which I am still ignorant. I have found it to extend in at least eight of these beyond the near degrees of parent and child, and brother and sister. Considering that the occurrence is so rare as to exist in only about one in every twenty-five or thirty males, these results are very remarkable, and their trustworthiness is increased by the fact that the hereditary tendency is on the whole the strongest in those cases where the Number-Forms are the most defined and elaborate. I give four instances in which the hereditary tendency is found, not only in having a Form at all, but also in some degree in the shape of the Form.
[PLATE III. HEREDTY IN NUMBER-FORMS]
Examples of an Hereditary Tendency to see Number-Forms, 4 Instances where the Number Forms in same family are alike 3 Instances where the Number-Forms in same family are unlike
Figs. 46-49 are those of various members of the Henslow family, where the brothers, sisters, and some children of a sister have the peculiarity.
Figs. 53-54 are those of a master of Cheltenham College and his sister.
Figs. 55-56 are those of a father and son; 57 and 58 belong to the same family.
Figs. 59-60 are those of a brother and sister.