EXPERIMENTS ON THE FORE LIMB OF AMBLYSTOMA 437 
which the dorsal half of the limb bud was removed (Rem. E. 27). 
This was a club-shaped appendage less than half length and 
without hand (fig. 15). The next most marked defect followed 
removal of the posterior half of the bud (H. R. E. 12-); here 
the forearm was slender and but one whole digit was developed, 
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Figs. 15 to 20 Outline views of defective limbs which developed after re- 
moval of portions of the limb bud. X17. 1, 2, 3, 4, ordinal number of the 
digits; d., reduplicating digit. Figure 15. Experiment Rem. E. 27 (dorsal half re- 
moved); lateral view right side, considerably foreshortened; twenty-six days 
after operation. Figure 16. Experiment H.R. E. 12—(posterior half removed) ; 
ventral view; twenty-six days after operation; the arrow points headward. 
Figure 17. Experiment Rem. E. 13 (posterior half removed) ; limb amputated and 
preserved twenty-seven days after operation; ulnar half of hand is very defective, 
but the limb which regenerated after amputation wasnormal. Figure18. Ex- 
periment Rem. E. 29 (posterior half removed) ; lateral view right side, arm much 
foreshortened; first digit (1) abortive and syndactylous with second, which has a 
reduplicating branch (2D); thirty-one days after operation. Figure 19. Experi- 
ment Rem. E. 21 (central portion of limb bud removed); limb amputated and 
preserved twenty-six days after operation; right limb lateral view. Figure 20. 
Experiment H. E. 21 — (anterior half removed); right side ventral view, eighteen 
days after operation; the arrow points headward. 
which, however, had a reduplicating branch (fig. 16). In an- 
other case of removal of the posterior half (Rem. HE. 13) only a 
single long digit and the stump of a second were developed, the 
hand being quite defective (fig. 17). Amputation of this in- 
complete limb, was followed, however, by the regeneration of a 
normally formed one. The two remaining cases showed defects 
