106 ROSS G. HARRISON 
ventral graft, the usual primary regulative result was vitiated by 
reduplication. The same was true in three cases of half -buds 
inverted on the opposite side of the body {het.dv.). Reduplica- 
tion, therefore, is not in itself a regulatory process, but leads 
merely to a condition where regulation may take place through 
the reduction of the disharmonic member. 
The question now arises, whether the experiments give any 
ground for assuming that there is anything teleological in Ihese 
regulatory processes. While there is no proof that regulation by 
rotation is not of this nature, it would be a mistake to draw any 
conclusion regarding it until the details of the process are better 
understood. With regard to regulation through reduplication 
and reduction, it is clear that mechanical factors are sufficient 
to account for the process. It is in the disharmonic combinations 
that secondary regulation is necessary to produce normal results. 
When this is not accomplished by rotation, reduplications almost 
always arise, and there are only two cases of single disharmonic 
Imibs among the orthotopic grafts. The disharmonic relation, 
which is brought about by the inversion of the anteroposterior 
axis of the lunb bud, is thus seen to be a factor of prune import- 
ance in the production of reduplications. It is not the only 
factor, however, for some reduplications have occurred in har- 
monic combinations, due probably to other disturbances at the 
time of operation. But quite aside from the latter, it would be 
wholly unjustifiable to assume that there is any causal relation 
between the possible utility of the process of reduplication for 
regulatory purposes and its frequent, or even ahnost universal, 
occurrence where it might lead to this result. What seems to be 
the condition that brings about regulation after the reduplicating 
bud has arisen is the chance placement of the latter in a position 
corresponding to that of the normal single limb. This relation 
is attended by a more advantageous situation with respect to 
blood and nerve supply than that occupied by the original bud, 
and in extreme cases this leads to the resorption or suppression 
of the latter. It is only in such cases that complete regulation 
takes place and these constitute but about 15 per cent of the 
total number of reduplications. 
