388 



PATTERNS AND PROBLEMS OF DEVELOPMENT 



the level of section, leaving a lateral opening into the esophagus. As Fig- 

 ures 1^2, A and B, show, there is a complete disk and tentacles at the 

 distal end of the body (D), either the original or a reconstituted oral end. 

 Distal to the lateral opening a partial disk and partial circle of tentacles 

 are reconstituted with a polarity opposed to the original {D') , and proxi- 

 mal to the opening another partial disk and tentacles with polarity in 

 the original direction but, of course, with an alteration of the original 

 polarity {D"). Distal to the opening, one side of the animal is bipolar, 

 and the partial oral end D' is a mirror image of D" and also of the cor- 



FiG. 132, yl-C— Mirror-imaging in reconstitution, A, B, in Harenactis attenuata (from 

 Child, 19096); C, schematic outline for Britchdreijachhildtingen; explanation in text. 



responding part of D (Child, 19096). Similar reconstitutions can, of 

 course, be produced in other forms. 



A large number of triphcations with similar mirror-imaging, mostly 

 appendages, have been described by Bateson (1894, chap, xx) and Przi- 

 bram (192 1 and earlier papers). Some of these have been produced ex- 

 perimentally by lateral partial section; others have been found as anoma- 

 lies. These triplications have been called Bruchdreifachbildimgen by Przi- 

 bram. He regards them as resulting from a lateral injury with reconstitu- 

 tion of distal parts from both distal and proximal surfaces of the injured 

 region, essentially like the case of Harenactis. Figure 132, C, indicates 

 diagrammatically the character of these triplications, the curvatures of 

 the triplicate distal parts representing the asymmetries. The mirror-imag- 

 ing is the same in D, D', and D" in Figure 132, ^, 5, and C, the only 

 difference between the Harenactis triplication and that of the appendage 



