17 Sets of Twins (A and B).
Comparison between the patterns on the Fore, Middle, and Ring-fingers respectively of the Right hand.
Agreement (=), 19 cases; partial (··), 13 cases; disagreement (×), 19 cases.
| A | B | A | B | A | B | A | B | A | B | ||||||
| Fore | 42 | = | 42 | 21 | = | 21 | 40 | = | 40 | 6 | = | 6 | 1 | = | 1 |
| Middle | 42 | = | 42 | 8 | = | 8 | 32 | × | 42 | 15 | ·· | 32 | 42 | = | 42 |
| Ring | 42 | = | 42 | 8 | = | 8 | 42 | = | 42 | 33 | = | 33 | 40 | × | 19 |
| Fore | 42 | = | 42 | 43 | × | 15 | 1 | = | 1 | 15 | × | 34 | 2 | ·· | 42 |
| Middle | 42 | = | 42 | 42 | ·· | 40 | 1 | × | 40 | 42 | = | 42 | 42 | = | 42 |
| Ring | 42 | ·· | 46 | 35 | = | 35 | 40 | ·· | 42 | 14 | × | 32 | 42 | × | 14 |
| Fore | 49 | ·· | 14 | 15 | × | 49 | 15 | ·· | 16 | 1 | × | 42 | 1 | × | 15 |
| Middle | 42 | = | 42 | 23 | × | 14 | 19 | × | 42 | 42 | ·· | 48 | 32 | × | 22 |
| Ring | 9 | ·· | 32 | 14 | ·· | 16 | 6 | ·· | 18 | 42 | × | 8 | 18 | × | 23 |
| Fore | 48 | × | 33 | (loop) | × | 9 | |||||||||
| Middle | 42 | × | 22 | 48 | × | 22 | |||||||||
| Ring | 14 | ·· | 6 | 9 | ·· | 35 | |||||||||
The result is that out of the seventeen sets (=51 couplets), two sets agree in all their three couplets of fingers; four sets agree in two; five sets agree in one of the couplets. There are instances of partial agreement in five others, and a disagreement throughout in only one of the seventeen sets. In another collection of seventeen sets, made to compare with this, six agreed in two of their three couplets, and five agreed in one of them. There cannot then be the slightest doubt as to the strong tendency to resemblance in the finger patterns in twins.
This remark must by no means be forced into the sense of meaning that the similarity is so great, that the finger print of one twin might occasionally be mistaken for that of the other. When patterns fall into the same class, their general forms may be conspicuously different (see [p. 74]), while their smaller details, namely, the number of ridges and the minutiæ, are practically independent of the pattern.
It may be mentioned that I have an inquiry in view, which has not yet been fairly begun, owing to the want of sufficient data, namely to determine the minutest biological unit that may be hereditarily transmissible. The minutiæ in the finger prints of twins seem suitable objects for this purpose.
Children of like-patterned Parents.—When two parents are alike, the average resemblance, in stature at all events, which their children bear to them, is as close as the fraternal resemblance between the children, and twice as close as that which the children bear to either parent separately, when the parents are unlike.
The fifty-eight parentages affording fifty couplets of the fore, middle, and ring-fingers respectively give 58 × 3 = 174 parental couplets in all; of these, 27 or 14 per cent are alike in their pattern, as shown by Table XXVIII. The total number of children to these twenty-seven pairs is 109, of which 59 (or 54 per cent) have the same pattern as their parents. This fact requires analysis, as on account of the great frequency of loops, and especially of the pattern No. 42 on the middle finger, a large number of the cases of similarity of pattern between child and parents would be mere random coincidences.