102 ROSS G. HARRISON 
experiments that it has been completely reversed by the opera- 
tion. The evidence points, on the contrary, to the mtroduction 
of another factor which is manifested also in the tendency of the 
individuals to show defects on the inner side (i.e., the side turned 
toward the partner). In the ease of the left-hand member, 
this acts in the same sense as the innate tendency to asymmetry 
of the viscera, while in the case of the right-hand member, it 
antagonizes, and in many cases, overcomes the latter. ^^^ Spe- 
mann suggests many different experiments to throw light upon 
this question. The interesting point in Spemann's discussion, 
in connection with the present work, is that the necessity for as- 
suming some sort of intimate structure to account for external 
symmetry relations is recognized. In the case of the redupli- 
cated limbs it is not clear whether the reversal of the secondary 
bud is a result of direct action upon the individual processes of 
development going on within it, or whether the influence of the 
primary bud actually reverses the intimate structure. If it 
should be found that the reaction takes place before the cells of 
the lunb blastema lose their totipotence, then the latter is 
undoubtedh'' true. Otherwise it may be that the differentiation 
in the limb blastema takes phice directly under the influence of 
the tissues of the environment. 
H. Form regulation and function in transplanted limbs 
That the limb bud after transplantation becomes adapted in a 
measure to the new conditions is obvious from a casual con- 
sideration of the experimental results. There are different types 
of adaptation, however, for although regulation of form and func- 
tion go largely hand in hand, in some cases there may be very 
complete functional regulation without form regulation,"^ and, 
particularly in the heterotopic grafts, form regulation without 
function. By form regulation is meant, in the present connec- 
tion, the process by which a limb bud that is implanted abnor- 
i"Cf. also Pressler ('11). 
'" For instance, in Experiment I. E. 64, the single disharmonic limb func- 
tioned very activel.v and effectivel3'. 
