SHOULDER GIRDLE AND ANTERIOR LIMB Seah 
almost complete absence of the shoulder girdle by transplanting 
a small area of cells (text fig. 1, smaller of the two circles) from 
the dorsal half of a typical limb dise (fig. 31). This area is 
practically free from girdle-forming cells. 
8. Either the dorsal or ventral half of the girdle rudiment 
may be transplanted along with the corresponding portions of the 
limb rudiment. In such cases complete limbs develop from the 
transplanted portion of its rudiment, while only that portion 
of the girdle develops corresponding to the part of the rudiment 
which has been implanted (Exps. B 2, B 3, and figs. 32 and 33). 
These results demonstrate the non-equipotentiality of the girdle 
system. 
9. The limb mesoderm is already determined in embryos in 
the stage of open medullary folds. The rudiment can be suc- 
cessfully extirpated and transplanted at this stage (tables 7 
and 8). 
10. In the absence of surface markings, the position of the 
limb mesoderm can be located quite accurately by covering the 
wound with ectoderm from an embryo, previously stained in a 
solution of Nile blue sulphate, and observing its relation to the 
later formed somites (text figs. 2 and 3). 
11. When typical limb buds the width of three and one-half 
somites in diameter (text fig. 1) are extirpated from embryos in 
the tail-bud stage, only the central portion of the girdle rudi- 
ment is included (Exp. A 4, fig. 10); but areas of equal size when 
extirpated from embryos in the stage of high medullary folds 
(text fig. 2) frequently include the entire girdle rudiment (fig. 17). 
12. Implanted girdles developing from areas of mesoderm, 
which are taken from embryos in the stage of open medullary 
folds, are considerably larger when compared with the normal 
than those which develop from areas of equal size taken from 
embryos in the tail-bud stage (cf. figs. 19, 20, 21 and 22). 
13. When double limbs arise from a transplanted rudiment, 
only one girdle is formed, which may have one or two shoulder 
joints, depending on whether or not the two members of the re- 
duplication are completely fused or partly separated at the base. 
