TRANSPLANTATION OF LIMBS IN AMBLYSTOMA 139 



shoulder-girdle was developed anterior to the isolated distal 

 portions of the intact suprascapula and coracoid, which always 

 develop in situ after a typical limb-bud excision. Further, 

 the fact that the anterior member lacked a girdle, except for 

 a very fragmentary coracoid, also indicated that the well- 

 developed girdle of the caudal member was developed from the 

 girdle rudiment included in the transplant. 



Previous limb experiments on Amblystoma have shown that 

 when supernumerary limbs develop from a single transplant 

 under conditions of normal orientation with respect to the sur- 

 rounding tissue, the one is always the mirror image of the other 

 (Harrison, '17, '21; Detwiler, '18), i.e., a disharmonic appendage. 

 In the light of these results, the anomalous reduplication in the 

 present experiment, if resulting from a single transplant as the 

 evidence favors, is an unusual phenomenon. Harrison ('21), 

 however, describes several cases with anomalous double-limb 

 formation, both of the same laterality, resulting from a composite 

 rudiment in the orthotopic position. The two limbs in these 

 cases are shown in Harrison's paper (I.e.), 79, figs. 131 and 132. 

 The combinations producing them are shown on page 70 of his 

 paper (combinations 10 and 11). 



In the case under consideration, the development of a well- 

 formed branchial bar between the bases of the two limbs might 

 have effected cleavage of the original transplanted rudiment, 

 resulting thereby in the development of the two limbs. It has 

 been shown by Harrison ('18) that, under normal conditions, 

 splitting the limb bud bj^ a vertical or horizontal incision never 

 produces reduplication. There is no apparent reason, however 

 why two portions of a transplanted limb rudiment, if permanently 

 separated, should not develop into two limbs of the same lateral- 

 ity. Such a result is normally produced when a portion of the 

 rudiment is transplanted: one limb will develop at the original 

 site and the other at the heterotopic position. 



In the present case the anterior limb developed in the posterior 

 region of the otic capsule. The shoulder-girdle consisted of only 

 a fragmentary coracoid. This was fused dorsally with the 

 cartilaginous capsule of the ear, which, together with the small 



