RECONSTITUTIONAL PATTERNS IN EXPERIMENT 393 



ters beyond the range of mutual influence may result in duplication with- 

 out mirror-imaging. 



A very different interpretation has been advanced by Przibram (1924, 

 1925, 1927). His view is that axiate pattern is definitively established in 

 the primordium at the time of transplantation, that apparent reversal of 

 asymmetry is not due to an influence of the host body or pattern but to 

 development from the proximal, instead of the distal, part of the trans- 

 plant. With persistence of the original asymmetry such a limb will be a 

 mirror image of a limb developing from the distal region of the limb bud, 

 just as a proximal hydranth or a posterior head or an isolated hydroid or 

 planarian piece is a mirror image of that at the distal or anterior end. 

 Such a limb would correspond to D' of Figure 132, C. Duplication would 

 result from development of a limb both distally and proximally from the 

 transplant, that is, from bipolar development with original asymmetry 

 in both polar axes. Triplication of hmbs Przibram interprets in terms of 

 the Bruchdreifachbildungen (p. 388), as limb development from distal and 

 proximal regions of the transplant and also from the limb bud region of 

 the host. It may be noted that Delia Valle (191 1, 1913) obtained the 

 axial relations of Figure 132, C, in regeneration from a partial transverse 

 section of the amphibian limb. 



As in so many biological controversies concerning interpretations, it 

 seems entirely possible that both views may be correct, that is, that 

 dupHcations and triplications of hmbs and their asymmetries may occur 

 in both ways and perhaps also a new center of limb development, that 

 is, a region of activation may sometimes originate in a region of less com- 

 plete union of transplant and host or of more intense irritation by the 

 operation. There are plenty of cases in which such factors do initiate 

 axiate development. It is well known that parts of limb primordia sec- 

 tioned in various directions may give rise to whole limbs. '"^ Limb-bud 

 mesoderm isolated from ectoderm and implanted with reversal of the 

 mediolateral axis, the longitudinal axis of the limb, results in development 

 of whole limbs which accord with the rules (Harrison, 1925a). Redupli- 

 cated limbs developing in heteroplastic transplants between Amhly stoma 

 species always have donor characteristics, according to Swett (1932). On 

 the other hand, Oka (1934) maintains that in Hynohius some cases of 

 duplication represent distal and proximal regeneration from the trans- 

 plant and that some triplications develop entirely from the transplant. 



'"Harrison, iQ2ia; Swett, 1924, 1Q26, 1928; Graper, 1926. 



