306 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
occurred along with the atrophy, partial or complete, of the functional 
digits, which apparently caused the subsequent development of the 
normally rudimentary ones. In these instances it would seem that the 
nutriment which is normally appropriated by the functional digits is 
transferred to, and utilized by, the digital rudiments, thus enabling 
them to continue their development. We are familiar with the same 
phenomenon in plants, where, if the terminal bud is removed, lateral 
buds, which would otherwise have remained dormant, are stimulated 
to development by the extra supply of nutriment which they receive. 
Again, polydactylism very often accompanies acephalic conditions, and 
other abnormalities due to defect of some organ, as recorded by 
Fackenheim and others. Here the same law is applicable ; on account 
of the abnormal absence of certain organic fundaments, the remaining 
ones receive more than their usual amount of nutrition ; as a result, an 
increased development of normally reduced or otherwise modified digits 
may be brought about. But these cases of polydactylism may also be 
explained as due to external influences acting in utero. Fackenheim has 
shown that in a certain family polydactylism did not appear as a correla- 
tive of inherited abnormality by defect, until one of its members married 
into another family in which digital abnormalities were of frequent occur- 
rence. Then only did offspring appear afflicted with both polydactylism 
and defective teeth. From such cases the evidence that excess of nutri- 
ment causes germinal variation loses much of its weight. 
Any explanation of the phenomena of germinal variation must neces- 
sarily be theoretical, as long as our practical knowledge of the germ-plasm 
is so limited. We know, however, that all neomorphs are prone to varia- 
tion. In polydactylism all the digital abnormalities produced by internal 
causes vary greatly, and the tendency to variation is inherited. By 
Mendel’s law the inheritance of these variations is explained, and the 
puzzling point which Wilson (96) attempted to clear up by his theory of 
nutritive variation, is made plain, — the fact that in man an individual 
having a polydactyle manus may produce offspring with abnormal pes or 
with all extremities abnormal. In this case we may assume that the 
variation first appeared on all extremities as a duplication of the mini- 
mus, due to the doubling of the determinants of these digits. On 
marrying with a normal individual the abnormal character would be 
dominant, but not completely so (Bateson found this to be the case with 
the polydactyle fowl). Of the DA offspring produced, some would be 
abnormal like the D parent, but in others the usually dominant character 
might be recessive ; their extremities might be entirely normal, or only 
