110 ROSS G. HARRISON 
('pointing') in the direction of what was originally the posterior 
pole of the anteroposterior axis. Thus, in two of the combina- 
tions (homopleural dorsoventral and heteropleural dordosorsal) 
they point anteriorl}^ or dorsoanteriorly, and in the two others 
(homopleural dorsodorsal and heteropleural dorsoventral) they 
point posteriorly or dorsoposteriorly like the normal. In the 
latter case the subsequent development is usually normal, bar- 
ring reduplication ; in the latter there is a tendency for the limb to 
stick out to the side and to rotate more or less from the position 
in which it would be found, were the position determined entirely 
by the orientation of the bud itself. 
3. The pahnar surface of the limb tends to develop on the side 
turned toward the body of the animal, and the ulnar border is 
dorsal, although the rotation mentioned in the previous para- 
graph tends to change these positions. 
4. The above circumstances determine the asymmetry of the 
limb as follows: when the dorsoventral axis is not inverted, the 
original prospective asymmetry persists; when the axis is in- 
verted, the asymmetry is reversed (rules 1 and 2, p. 4). In more 
general terms: the asymmetry of the limb is determined by two 
factors, the polarization of the anteroposterior axis of the lunb 
bud and the orientation of the Imib bud with respect to the dorso- 
ventral polarization of its organic environment (figs. 2 and 135). 
5. In two of the combinations (homopleural dorsodorsal and 
heteropleural dorsoventral) the asymmetry of the limb which 
de\'elops corresponds to that of the side of the body on which it is 
placed (harmonic); in the other two (homopleural dorsoventral 
and heteropleural dorsodorsal) it corresponds to that of the oppo- 
site side (disharmonic) . 
6. Duplex and multiplex limbs arise frequently from the trans- 
planted buds. They are of all grades and kinds and occur in 
different proportions in the several experiments. In the hetero- 
topic grafts they are more frequent in the harmonic combinations, 
while in the orthotopic position they are much more frequent in 
the disharmonic combinations. 
7. In nearl}^ all cases one member of a pair or group can be 
distinguished as the original (prmiary) and the other one or ones 
