RECONSTITUTIONAL PATTERNS IN EXPERIMENT 389 



being that in the former D' and D" are partial symmetries developing 

 in relation to the anatomy of the original individual, while in the latter 

 the asymmetries of the reconstituted parts are complete, even though 

 they develop from surfaces of partial section. 



Przibram interprets these triplicate forms in terms of a hypothetical 

 space lattice {Raumgitter) in the protoplasm. In terms of the gradient con- 

 cept, activation of the two surfaces by section or injury is sufficient to 

 determine a new polar gradient on each. With outgrowth of new tissue 

 each becomes the distal part of an appendage, the parts regenerating 

 being those normally distal to the level of the appendage from which re- 

 generation takes place, though in some cases not all of these develop. 

 Evidently the polarity of D' originates independently of the polarity of 

 the region from which it develops; and if the preceding analysis of recon- 

 stitution is not wholly mistaken, the polarity of D" is also independent 

 of that of the region from which it develops. The asymmetries of the re- 

 generates, D' and D" , however, are the same as the asymmetry of the 

 region from which they develop, except that their asymmetry may be 

 complete and normal, although they develop from a surface of partial 

 asymmetry. Apparently the partial asymmetry differential at the surface 

 from which regeneration takes place is sufficient to determine a complete 

 asymmetry in the new tissue. 



The regenerated axes, D' and D" , do not usually develop parts proxi- 

 mal to the level from which they arise. In the case of D" these parts 

 are already present; as regards D' , if the high end of the gradient is distal 

 and development progresses proximally, it is balanced and its further 

 progress prevented by the similar opposed axis D; if development pro- 

 gresses distally from the surface of section or injury, development of distal 

 parts is probably determined by the activation adjoining that level; if 

 the high ectodermal region is distal and that of the mesoderm proximal, 

 both these factors may be concerned in determining the result. The scale 

 of organization of D' is often smaller than that of D, probably in conse- 

 quence of more or less inhibition of the new gradient by D. A similar 

 difference in scale appears very often in bipolar partial forms of hydroids 

 and planarians, the proximal hydranth or partial hydranth and the pos- 

 terior head being smaller and less fully developed and sometimes repre- 

 senting a smaller part of the polar axis than the distal hydranth or the 

 anterior head. 



