8 
ROSS G. HARRISON 
which they are placed (fig. 2), for the non-inverted limb bud 
from the same side {ho7n.cld.) does not have its prospective asym- 
metry changed while the inverted limb bud from the opposite 
side {het.clv.) does. The limbs which develop in these combina- 
HOM. 
D-D 
HON. 
0-V 
HET. 
D-D 
H£T. 
V 
Fig. 1 Diagram showing the eight different operations. The outline of an 
Amblystoma embryo in the operating stage is shown above. The circles within 
it represent the limb bud, in the normal (orthotopic) and the abnormal (hetero- 
topic) location. The four circles below represent the four different ways in which 
limb buds may be oriented with reference to the cardinal points of the embryo; 
the letters {D, dorsal; T', ventral; A, anterior, and P, posterior) within the 
circles designate the original cardinal points of the transplanted limb, those 
outside the corresponding points of the embryo. The operations are represented 
to be on the right side. R, right limb bud; L, left limb bud; horn., homopleural; 
het., heteropleural. 
tions thus fit in with their surroundings; they have therefore been 
called harmonic. The other two combinations (homopleural 
dorsoventral and heteropleural dorsodorsal) give rise to limbs 
of the side opposite to that of their seat of implantation, for the 
inverted bud from the same side (hom.dv.) has its asymmetry 
reversed, while the non-inverted bud from the opposite side 
