SYMMETRY IN TRANSPLANTED LIMBS 97 
tion of a simple regenerating bud. This harmonizes with 
Driesch's ('06) observations on double Echinus embryos. 
In the present work, the reduplicated extremities are nearly 
all found to be in minor symmetry, and many of those in which 
three members are present, if seen only in the fully developed 
condition, would appear to be cases of paired supernumeraries, 
conforming, though with some aberration, to Bateson's rules. 
The individual histories show, however, that they are mosth- 
simple duplicities in which the supernumerary mirrors the orig- 
inal, and this seems to be the case in Braus's experiments, too. 
Two reduplicating limbs often do develop, but usually each grows 
as a bud from the original instead of the two arising as a pair in 
themselves. Each of them mirrors the original limb, so that the 
two supernumeraries are both of the same side. In other cases 
the supernumeraries are themselves double, in which event there 
is strict conformity to Bateson's rule, but the former constitute 
a large majority, and conformity there is only superficial, for the 
original limb is the middle member and not one of the extremes. 
In view of these facts, there is probably no very fundamental 
difference between the two classes of reduplications, i.e., between 
the double supernumeraries symmetrical with each other and the 
single supernumerary symmetrical with the original; had Bate- 
son had the developmental stages at his disposal, he himself 
might not have drawn so sharp a distinction. 
In accordance with the above, Bateson's rules might be stated 
in more general form, so as to include both simple dupHcities and 
symmetrical pairs, as follows: 
1. The long axes of duplex or multiplex appendages lie in one 
plane. 
2. Two adjacent members form in structure and position the 
image of each other, as reflected from a plane mirror bisecting 
the angle between the respective axes and perpendicular to the 
common plane of the two axes (figs. 3 and 4). 
The present experiments show (tables 2, 3, 5, and 8) that, 
excepting heterotopic grafts, it is in the disharmonic combina- 
tions that reduplications are most frequent. What, now, is the 
nature of the disturbance that causes the doubling of transplanted 
