THE RECONSTITUTION OF ISOLATED PIECES in 



which varies with the condition of the animal, with the level of the 

 body from which the piece is taken, and with various external 

 factors which influence the rate of metaboHsm, do not produce 

 complete normal animals, although they may undergo a greater 

 or less degree of reconstitution and approach more or less closely 

 to the normal form. Such pieces show all gradations between the 

 normal animal at one extreme and a completely headless form at 

 the other (Child, 'iib, 'iic, '12b). It has been found convenient 

 to distinguish in this graded series of forms five different types, as 

 follows : 



Normal. — The head is like that of animals found in nature with 

 two completely separated eyes and cephalic lobes at lateral margins 

 (Fig. 17). 



:md (M) cno 



Fig. 20. — Various degrees o£ teratophthalmia in Planaria dorotocephala 



Teratophthalmic. — The head is of the usual form, but the eye 

 spots show differences in size, asymmetry in position, approach to 

 the median line, or various degrees of fusion. Some of the eye 

 forms are shown in Fig. 20. In all teratophthalmic animals the 

 cephalic ganglia show various degrees of fusion or asymmetry, the 

 condition of the eyes being to a considerable extent indicative of 

 that of the ganglia. 



Teratomorphic. — Here the preocular region of the head fails to 

 attain its full size or does not appear at all. Consequently the 

 cephalic lobes arise on the anterior margin of the head as in 

 Fig. 21 A, or in extreme cases are fused together in the median line 

 at the front of the head (Fig. 21 5). 



