io6 INDIVIDUALITY IN ORGANISMS 



extent and so to control it experimentally in various 

 ways, and my experiments have led to certain conclusions 

 concerning the nature of reconstitution. A part of the 

 evidence on which these conclusions are based has 

 already appeared in various papers,' but some of it is still 

 unpublished. Here only some of the more important 

 points and the conclusions are briefly presented. The 

 results of the reconstitution of pieces in Planaria doro- 

 tocephala differ widely in different cases. I have found 

 it convenient to distinguish five different forms: the 

 normal (Fig. 50, p. 103), an individual in all respects 

 like the type of the species; teratophthalmic (Fig. 54, 

 A, B), in which the eyes show various degrees of fusion, 

 inequality, or other departures from the usual condition, 

 but the head as a whole shows the usual form; terato- 

 morphic (Fig. 55, A, B), usually with a single eye in the 

 median line and the cephalic sensory lobes more or less 

 approximated or completely fused at the front of the 

 head instead of in a lateral position; anophthalmic 

 (Fig. 56, A, B), with an outgrowth more or less like a 

 head and containing a small ganglionic mass, sometimes 

 with cephahc lobes fused at the front, but without eyes; 

 headless (Figs. 52, 83, p. 103), in which the cut end 

 merely heals without outgrowth of new tissue. Differ- 

 ent degrees of development of the cephalic ganglia 



' Child, 'Studies on the Dynamics of Morphogenesis, etc., I," 

 Jour, of Ex per. ZooL, X, 1911; II, ibid., XI, 1911; IV, ibid., XIII, 1912; 

 VII, ibid., XVI, 1914; VIII, ibid., XVII, 1914. See also Child, "Experi- 

 mental Control of Morphogenesis in the Regulation of Planar^'a" 

 Biol. Bull., XX, 191 1 ; "Certain Dynamic Factors in Experimental 

 Reproduction and Their Significance for the Problems of Repro- 

 duction and Development," Archiv fUr Entimckelungsmechanik, XXXV. 

 1913 



