442 ROSS G. HARRISON © 
fective to reveal its laterality. This case differs from the three 
described above in which the hand is symmetrically reduplicated, 
one member being a right and one a left, following the rule of 
mirroring. It is probably of a fundamentally different nature . 
from the others in that the posterior member obviously arose from 
the remaining half of the limb bud after operation, while the an- 
terior one regenerated from the anterior border of the wound, 
the two remaining far enough apart not to influence one another. 
In the ease of the true reduplications, the two members presum- 
ably arise from a single center which later doubles symmetri- 
cally. The other two cases of reduplication are not important. 
One (Rem. E. 18) involved the first digit only (fig. 35), and the 
other (Rem. E. 16) the second digit (fig. 36). 
In three cases the abnormal appendages which developed were 
amputated between the shoulder and elbow. One of them 
(Rem. E. 13, with a very defective hand with only one digit 
(fig. 17) ) and another (R. E. 18 with a reduplicated and a de- 
fective digit (fig. 35) ) regenerated normal limbs (fig. 37). The 
other failed to regenerate. These experiments show that such 
anomalies can hardly be due to the removal of specific organ- 
forming tissues from the rudiment. 
The anomalies are summarized in table 7. From this tabula- 
tion it is seen a) that defectiveness of the first digit may occur 
after removal of the posterior or the ventral halves or the cen- 
tral portion of the limb rudiment; b) that defectiveness of the. 
whole hand may arise after removal of the anterior, posterior, or 
dorsal halves; and c) that abortive limbs may occur after removal 
of any of the four halves. As for the reduplications, those of 
major degree are confined to operations on the anterior half of 
the limb bud. Minor reduplications, affecting the digits only, 
occurred in one case after each of three different operations. 
It would require a number of experiments many times that in- 
cluded in the above table to give statistical value to the num- 
bers in the several categories, and it is not likely that these can 
be done in the near future. Possibly the repetition of the ex- 
periments on a large scale might show, for instance, a relatively 
high proportion of defects in digits after removal of the posterior 
