SYMMETRY IN TRANSPLANTED LIMBS 69 
D. Transplantation of half buds 
Partly as a further test of the question of equipotentiality and 
partly to study more thoroughly the effect of harmonic and dis- 
harmonic combinations, a series of experiments with half limb 
buds was instituted. Instead of removing the whole circular 
disc comprising the limb rudiment, a semicircular piece was cut 
out, the wound bed carefully cleaned, and the removed portion 
replaced by a piece of similar size and shape from another limb 
bud. Considering only vertical and horizontal halves and re- 
placing vertical only with ^'ertical and horizontal only with hori- 
zontal, there are sixteen different experiments possible, which 
have been numbered in the diagram (fig. 120) from 1 to 1(5. 
There are five different pairs of attributes, which appear as 
alternatives in the operations. Thus the transplanted half bud 
is either — 1) homopleural {hom.) or heteropleural (het.); 2) up- 
right {dd.) or inverted (dv.); 3) homogeneous (homogen.) or hetero- 
geneous (heterogen.)', 4) vertical (vert.) or horizontal (horiz.); 5) 
anterior (ant.), dorsal (dors.) or posterior (post.), ventral (vent.). 
This aggregation would consist of 2-' or thirty-two classes, were 
it possible to combine the attributes of operation independently 
without restriction, as would be the case were the pieces rectangu- 
lar. Since, however, they are semicircular they fit in only half 
the cases, and the total is therefore reduced to sixteen. All of 
the possible experiments have been performed. 
If both halves of the disc are considered movable, further pos- 
sibilities open up. There would then be thirty-two different com- 
binations, which, however, in eight cases would be practically 
identical with the experiments where the whole disc is transplanted. 
None of these experiments have been performed, since the tech- 
nical difficulties would be at least doubled, and, as far as the 
study of either of the questions at issue is concerned, they would 
offer no advantage over those in which only one half of the bud is 
transplanted. Again, were the limb disc homogeneous, either or 
both halves could be turned inside out and then one hundred 
and twenty-eight different combinations would be possible. 
These are precluded, as in the case of the whole discs, by the 
