178 



PATTERNS AND PROBLEMS OF DEVELOPMENT 



oreceptors) on lateral margins of the head at a level slightly posterior 

 to that of the eyes. The head form is shown in Figure 63, ^, a transverse 

 section of head and ganglia at eye-level in Figure 64, A. 



The teratophthalmic head : In animals developing from pieces of equal 

 length from the same body-level of the parent teratophthalmic heads are 

 usually slightly smaller than normal heads and often less sharply pointed 



>1) CM) (H) CM) (X4) 



(M) iT^) (m (M) ;*; (M) 



Fig. 63, A-L.^The inhibition series of head forms of Diigesia dorotocephala. A, normal 

 head; B, teratophthalmic head; C, eyes of teratophthalmic heads; D-G, teratomorphic heads; 

 H-J, anophthalmic heads; K, L, acephalic forms. 



anteriorly and shorter, at least in earlier stages. The eyes are localized 

 nearer the median line than normally, and the pigment cups are more or 

 less connected; all degrees of approximation, even to complete cyclopia, 

 occur in these forms (Fig. 63, B, C). The two eyes are sometimes unequal 

 and localized at somewhat different levels, but these irregularities ap- 

 parently result from incidental differences on the two sides of the piece ; 

 for example, the presence of an intestinal branch at the level of section 



