PHYSIOLOGY OF RECONSTITUTION OF PLANARIA LATA. 



127 



dition. The members of this series fall readily into the same types 

 or groups as in the case of P. dorotocepltala (Child, 'no, '21), 

 viz., normal, teratophthalmic, teratomorphic, anophthalmia ace- 

 phalic. The normal head is like the head of Fig. 1. The terat- 

 ophthalmic head is normal in outline, but the eyes are more or less 

 approximated to the median line and the pigment spots are often 

 partially united or even fused (Figs. 12, 13). In the terato- 

 morphic head there is a single, or apparently single, median eye 

 and the anterior region between the cephalic lobes is incompletely 

 developed, so that the lobes appear more or less anteriorly or fused 

 at the median line (Figs. 14, 15). The anophthalmic head is 

 merely an outgrowth of tissue without eyes (Figs. 16, 17), and in 



OO OK) 



13 



16 



18 



19 



20 



Figs. 12—20. Forms resulting from reconstitution : Figs. 12, 13, teratoph- 

 thalmic heads and eyes: Figs. 14, 15, teratomorphic heads; Figs. 16, 17, 

 anophthalmic heads; Fig. 18, acephalic form; Fig. 19, tailless form; Fig. 

 20, biaxial heads. 



the acephalic form the anterior end simply heals over without out- 

 growth (Fig. 18). As regards degree of development, the ce- 

 phalic ganglia of these forms also constitute a continuous series from 

 normal ganglia in the normal head to a rudimentary ganglion in 



