TRANSPLANTATION OF LIMBS IN AMBLYSTOMA 



147 



April 25. Animal preserved (fig. 29, cf. fig. 28). Very abnormal, 

 functionless limb which is fused dorsally with an extension of gill ecto- 

 derm. Three abortive gills situated ventral to the gill shelf. 



The gill-producing potentiality of the outlying ectoderm is well 

 illustrated in the above cases. In all of these experiments the 

 entire ectodermal and mesodermaL tissues of the gill swellings 

 were removed prior to implantation of limb, yet one or more gills 



Fig. 28 Drawing of left lateral aspect of case AA2S64. Animal preserved 

 thirty-six days after operation. X 7. 



Fig. 29 Drawing of right lateral aspect of case AA2S64 (fig. 28). Fore-limb 

 rudiment transplanted into gill region as described in table 1 B. Gill ectoderm 

 dorsal to abortive limb (L) has migrated out on the limb and is fused along its 

 dorsomesial surface. Three very small external gills (EG) have developed out of 

 the tissue ventral to the normal gill region. X 7. 



developed in all four cases. From the results of these cases, as 

 well as from others not reported, the evidence indicates that the 

 ectoderm lying ventral to the typical gill region possesses a rela- 

 tively stronger gill-forming capacity than does that lying an- 

 terior and dorsal. In the majority of cases the gills developed 

 ventral to the gill region in approximation to the general heart 

 area as illustrated in figures 24, 26, and 29. This observation 

 supports the results obtained by Ekman ('13 b, p. 578, vide 

 supra, p. 125). 



