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ZOOLOGY: R. G. HARRISON 
but ultimately assumed normal posture by rotation. 6 cases (26%). 
The latter, which constitute the only exception to the rules, require 
further investigation. 
3. Heteropleural dorso-dorsal transplantations yielded: (a) Single 
non reversed limbs. Rule 1; one case only, and that not perfect (3%). 
FIG. 2. 
Diagram showing the results of the four operations, heterotopic or orthotopic, repre- 
sented as on the right side of the embryo. The circles indicate the transplanted limb buds, 
the letters having the same significance as in figure 1. Thus the two upper figures in the 
diagram represent homopleural, and the two lower ones heteropleural transplantations. 
The two on the left show the transplanted bud in upright (dorso-dorsal) orientation while 
the two on the left are inverted (dorso-ventral). The limbs which develop are shown in pro- 
file, the ulnar border being uppermost (dorsal) in all which actually develop. A heavy out- 
line indicates the primary member, a light outline the reduplicating one. It is to be noted, 
however, that the latter develop in by no means all cases while the former may be resorbed 
in the heteropleural dorso-ventral combination leaving only the reduplicating member pres- 
ent. The broken outlines show the posture that the limb would have assumed, had it de- 
veloped as a self differentiating member totally independent of the influence of its 
surroundings. 
(b) Reduplicated limbs, in which the secondary member, being re- 
versed, has the laterality of its new surroundings. Rule 3; 26 cases 
(78.8%). (c) Cases similar to the above (b) in their early develop- 
ment but differing later in that the reduplicating bud gained the upper 
hand and developed into a normal functioning limb of reversed laterality 
