500 S. R. DETWILER 
ally approximated each other until, in a larva which was kept 
alive eighty-five days after operation, they had become united 
into a single cartilage. 
The formation of the suprascapula and coracoid in the absence 
of the glenoid portion of the girdle demonstrates that their rudi- 
ments are already determined at the time of the operation, and 
that, while they eventually grow together, their unremoved rudi- 
ments are nevertheless not capable of restoring the missing parts, 
viz., the scapula, all or only a portion of the procoracoid, and the 
shoulder joint, the rudiments of which are removed in a typical 
limb-bud extirpation. 
Braus (’09) further found that when a limb bud is transplanted 
to a heterotopic position, a complete shoulder girdle of one-third 
to two-thirds the size of the normal develops at the place of 
implantation. From this he concluded (page 271) that the 
shoulder-girdle rudiment constitutes an Suiniotoimernic) restitu- 
tion system. 
According to this conclusion, totipotency is restricted to those 
girdle-forming cells which become implanted along with the limb 
bud, for, as has already been pointed out, the unremoved blas- 
tema can develop only into those parts the rudiments of which 
are already determined at the time of operation. The forma- 
tion of a reduced girdle, with all its components, from cells 
which, in the normal environment, give rise to only the more 
central parts, would show that in their normal surroundings their 
prospective potency is greater than their prospective significance. 
The results of the experiments set forth in this paper seem 
to necessitate for Amblystoma, however, an interpretation dif- 
ferent from that which Braus placed on the results of his 
experiments. 
This investigation was taken up at the suggestion of Prof. 
R. G. Harrison. It gives me pleasure to express here my thanks 
to Dr. Harrison for the guidance he has given me during its 
completion. 
