SYMMETRY IN TRANSPLANTED LIMBS 1 13 
ations, provided the combination is harmonic: 1) extirpation of 
any half of the bud; 2) fuvsion of two whole buds; 3) combination 
of two like halves, the other half being entirely missing; 4) inver- 
sion of the Imib bud; 5) inoculation of mesoderm cells from the 
limb under the skin in some other region of the embryo. 
19. Except for the circumstance that the dorso ventral differen- 
tiation of the Imib bud is a function of the orientation of the bud 
with respect to its organic enviromnent, the limb bud is a highly 
specific self-differentiating system. Its definitive form must, 
therefore, be represented in the organic elements (intimate struc- 
ture) of the Imib rudiment. 
20. One quality of these elements is their polarization, as 
shown by the definite relation to the direction of out-growth, 
assumed by the anteroposterior axis of the limb bud. It is sug- 
gested that the asymmetry of the limb rudiment and of other 
similar systems may be gradually brought about by the change 
in constitution of the structural elements in a manner similar to 
the building up of asymmetric molecules in organic compounds. 
21. Reduplications are produced as a result of that funda- 
mental attribute of living matter, the power to divide (Bateson) . 
They are induced, in the case of the limb bud especially, by a 
disharmonic relation between graft and host. 
22. There is no fundamental distinction between double super- 
numerary limbs constituting a sjanmetrical pair and the single 
supernumerary symmetrical with the normal one with which it 
is assQciated. Bateson's rules may be stated in simplified form 
in accordance with this conclusion (p. 97). 
23. Exceptions to Bateson's rule regarding symmetry rela-' 
tions of supernumerarj^ parts are verj^ rare. Those found in the 
present study, where two limbs of the same side occurred in linear 
series, are probablj' due to the appendages having been far 
enough apart not to influence one another in development, and 
at the same tune having been under the influence of the same 
organic environment. 
24. Review of the data on regeneration of supernumerary 
appendages shows that the reversal of asymmetry in one of the 
members of an enantiomorphic pair is not dependent upon the 
