SYMMETRY IN TRANSPLANTED LIMBS 103 
mally in relation to the embrj^o as a whole becomes adjusted so 
as to give rise to a linib in harmony v\'ith its new surroundings. 
Perfect adaptation is attained, however, only in cases where there 
is functional adaptation as well, i.e., only when both form and 
function are adjusted to the organism as a whole, and this occurs 
only in the orthotopic position or in positions very close to it. 
Functional ^regul^,tion is here largely a question of innervation, 
and, inasmuch as this has been made a subject of special investi- 
gation by Detwiler ('19, '20), it will not be considered at present 
further than is necessary in its relation to form regulation. 
Considering only the orthotopic grafts, there is no a priori 
ground for expecting any of the combinations to yield normally 
functional limbs except the homopleural dorsodorsal group, in 
which the axial i elations of the transplanted bud remain normal 
with respect to the cardinal points of the embr}-©. Nevertheless, 
it has been found that inverted limb buds from the opposite side 
of the body yield ahnost as high a proportion of normally formed 
and normally functional limbs as the first-named group. This 
phenomenon has been interpreted as due not so much to a sec- 
ondary regulation as to the structure of the elementary units of 
the limb bud, which are supposed to be symmetrical or reversibly 
differentiated (p. 89) along their dorsoventral axis. With an 
equal number of experunents in each of the four groups and with- 
out any disturbing factors, the primary processes of regulation 
should therefore lead, in accordance with the fundamental rules 
of symmetry, just as often to adaptive (harmonic) as to non- 
adaptive (disharmonic) end results, but not more often. This 
proportion is, however, exceeded by nearly 20 per cent of the 
expectancy, so that, taking the orthotopic experiments as a 
whole, 59.6 per cent yielded normally functioning limbs in normal 
posture, while 40.4, for the most part reduplications, were non- 
adaptive or only imperfectly adaptive (table 7) . The proportion 
is ahnost the same in the three classes of experiments, whether 
with whole buds after extirpation of the normal bud, with super- 
posed buds, or with half-buds, though, as more fully discussed 
below (p. 107), it is quite different in the heterotopic grafts. 
