EXPERIMENTS ON THE FORE LIMB OF AMBLYSTOMA 4053 
May 20. Transplanted tissue growing well, ‘points’ anteriorly. 
May 22. Growth considerable; reduplication beginning near base. 
May 25. Limb consists of two almost equal parts branching near 
base; anterior member is bidigitate. 
June 1. A perfect limb with reduplication of forearm and manus. 
Both members are tridigitate, with indications of fourth digit (fig. 42). 
The anterior member (PRIM.) which is the primary one, is a perfect 
left (original laterality of the tissue), the other (DUPL.) a right. 
June 6. Larva preserved. 
The specimen was cut into serial sections. The coracoid portion of 
the shoulder girdle is well developed and the glenoid fossa is marked. 
Dorsal to the joint there is no cartilage. Well-developed muscles run 
from the coracoid to the humerus, but the upper arm is almost de- 
void of muscle fibers. On the other hand, the forearm muscles are 
well developed. No nerve fibers have been found, 
Experiment Tr. Mes. 17. May 19, 1914. Mesoderm of left fore- 
limb to right side. 
May 25. Transplanted bud sticks out almost straight from side of 
body. 
June 1. Limb has grown considerably, but will probably be defec- 
tive as to digits. 
June 6. Unchanged. Limb cut off just below elbow. 
June 29. Larva has grown well. Limb healed, but no hand has de- 
veloped. It shows the elbow bend and has the posture of a normal 
right limb (fig. 43). 
Experiment Tr. Mes. 18. May 19, 1914. Mesoderm of left limb- 
bud to right side. 
May 20. Healing perfect; transplanted tissue a good nodule. 
May 22. Nodule increasing markedly. 
May 25. Transplanted tissue growing and points toward tail. 
Figs. 38 to 43 Amblystoma larvae showing supernumerary limbs developed 
from inoculated mesoderm cells of the limb bud. X 7}. Figure 38. Experi- 
ment Tr. Mes. 1; the supernumerary limb is primarily a left (from left-handed 
tissue), but the hand is symmetrically reduplicated; sixteen days after opera- 
tion. Figure 39. Experiment Tr. Mes. 4; supernumerary limb, primarily a 
left, though the inoculated tissue was from the right side; irregularities in the 
digits; twenty-seven days after operation. Figure 40. Same experiment, ven- 
tral view. Figure 41. Experiment Tr. Mes. 5; the supernumerary limb is a 
nearly normal left developed on the right side of body from tissue of right side. 
The only abnormality is the syndactyly of the first two digits; twenty-seven days 
after operation. Figure 42. Experiment Tr. Mes. 16. Ventral view of larva 
showing supernumerary limb reduplicated from elbow down; PRIM., primary 
member, a left (from left handed tissue); DUPL., secondary member, a right; 
twenty-four days after operation. Figure 43. Experiment Tr. Mes. 17. Super- 
numerary limb regenerated after amputation, a right (from left-handed tissue) 
with abortive hand; forty-one days after inoculation, twenty-three days after 
amputation. 
