324 
can be inhibited or suppressed as the 
result of the presence of other factors. 
In poultry,” he continues, “‘we know by 
experiment that the presence of an extra 
toe may behave as a dominant, following 
the simple rule with fair regularity, but 
in other families the number of domi- 
nants produced is too small and trans- 
mission may occur through normals des- 
titute of extra toes. Such facts point 
to the existence of some unknown com- 
plications in those families.” 
POLYDACTYLISM ,IN MAN 
In man it is well known that an extra 
finger or toe sometimes appears; but 
as we know of no ancestor, within hun- 
dreds of millions of years, who had more 
than five, human polydactylism can not 
be like that of the guinea-pig—the ap- 
pearance of an ancestral character. It 
may, therefore, most conveniently be 
assumed to be due to a splitting of one 
or more of the ordinary digits, which 
may be so extreme in degree that the 
individual possesses a “double hand”’ 
of 10 fingers attached to one wrist. The 
most ordinary type consists of the pres- 
ence of one extra finger, as is shown in 
the Italian immigrant whose hands were 
photographed at Ellis Island, N. Y.., 
recently (figs. 17, 18). Dr. Howard A. 
Knox, assistant surgeon of the U. S. 
Public Health Service, who sent in these 
photographs, calls attention to the in- 
teresting feature of the case—that the 
extra fingers function completely, each 
having fully developed joints and tend- 
ons. They seem to have been produced 
by a division of the little fingers in two. 
Dr. Knox investigated the family 
history of the immigrant as far as was 
possible, and found that one uncle 
(probably maternal, but there is doubt 
on this point) has an extra digit on the 
right hand only. But its location was 
the same as that in the subject here 
The Journal 
of Heredity 
shown. The immigrant’s second son, 
about 23 years of age, has one extra 
digit on each hand and each foot. 
Such a family history is fairly typical 
of most of those which describe poly- 
dactylism in man. The condition re- 
appears in almost every generation, but 
it is frequently not quite the same, and 
appears to be distributed without regard 
to any regular form of procedure. 
Davenport shows this plainly, despite 
his optimistic expression, when he writes, 
“The peculiarity of supernumerary fin- 
gers and toes is one that is inherited in 
nearly typical fashion. I have worked 
extensively on polydactylism in fowls 
and there can be little doubt that the 
character behaves the same way in man. 
The extra toe is due to an additional unit 
so that when one parent has the extra toe 
the children will also have it. However, 
it sometimes happens that the offspring 
fails to produce the extra toe; but such 
persons, becoming in turn parents, may 
produce the polydactyl condition again. 
. The eugenical conclusion is: poly- 
dactyl persons will have at least one- 
half of their children polydactyl. Those 
quite free from the trait, though of the 
polydactyl strains, will probably have 
only normal children.”’ 
This conclusion may be a rough ap- 
proximation to what usually happens, 
but it cannot be held to be an exact 
statement of the mode of heredity of 
polydactylism. Nor is any one in a 
position at present to give such an 
exact statement. We can only say that 
the appearance of extra fingers or toes 
(they frequently go together) is inherited 
to a high degree, but without any dis- 
coverable regularity. Fortunately, the 
trait is one that possesses no eugenic 
significance, and we can therefore view 
our ignorance with more complacence 
than if the trait really possessed im- 
portance to the race. 
Origin of the White Blackberry 
The white blackberry put in the 
trade by Luther Burbank some years 
ago 1s a good example of the production 
of a marketable fruit by the recom- 
bination of existing characters. The 
parents are said to be Lawton’s black- 
berry and an insignificant cultivated 
bramble of the eastern states. The 
latter has pale amber berries and is 
probably an albino variety of the same 
species of blackberry as _ Lawton’s. 
Burbank crossed the two and selected 
from the progeny (presumably in the 
second generation) individuals that pos- 
sessed the shape and qualities of the 
Lawton and the color of the bramble. 
