Experiments with other Mammals 117 
number of black lambs is too small on the assumption that 
chance meeting of equipotent “pure” germ-cells brings about 
the results. 
Poulton * has given some records of polydactyl cats that appear 
to be explicable, so far as they go, along Mendelian lines. Three 
young were produced from a polydactyl female by an unknown 
father. They were all polydactyl. If polydactylism dominates 
over the normal condition, this result is simple dominance. One 
of these individuals (Ff) produced three litters (by unknown 
fathers), in which four normal and six abnormal kittens ap- 
peared. If the father was normal, five normal and five poly- 
dactyl young would be expected. Thus: — 
P+N 
N+N 
2NP+2NN 
Only two kinds of discontinuous inheritance that may possibly 
follow Mendel’s law have been shown for man. Albinism, ac- 
cording to certain data collated by Castle, may perhaps follow 
this rule. The cases referred to were albino negroes. Albinism is, 
of course, different in this respect from white. In the latter case, 
blending of the black and white occurs to produce mulattoes. 
The other case is that of polydactylism. Fachenheim has 
given some statistics,” that Davenport has examined from the 
point of view of Mendelism. The accompanying table gives the 
inheritance through three generations : — 
Gen. NxP 
| | 
I, b ¥ Na Pen) Noa) aka AGN) | re 
II. 6N3P4N3P 7N3N 2P8N 2P ee 
2N 3P 
Si sy N ie ae 
wzaN3N2P 3N N 
1 Nature, 1883. ? Jena Zeitschrift, XXII, 1888. 
