192 MARGARET R. HAASE. 



EXPLANATION OF FIGURES. 

 PLATE I. 



FIG. i. Ventral aspect of Prorhynchus stagnalis to show especially the lateral 

 expansion (I.e.) of the exploratory region anterior to the ciliated pits (c.p.). Chitini- 

 ous penis (ch.p.) ; pharyngeal sac (ph. s.) ; pharynx (ph.); penis bulb (p. b.); enteron 

 (en.); seminal vesicle (s.v.); vas deferens (v.d.); egg about to be liberated (e.); 

 ovary (ov.) ; testes (t.) ; opening of female reproductive organs ( 9 ) ; (Modified from 

 Von Graff). 



FIG. 2. Dorsal aspect of anterior third of body to show relation of ciliated pits 

 (c.p.) to central nervous system. Pharyngeal sac (ph.s.); pharynx (ph.); dorsal 

 commissure (d.c.); right dorsal ganglion (d.g.); right anterior nerve (a.n.); right 

 posterior nerve (p.n.). 



FIG. 3. Right lateral aspect of anterior third of body to show relation of ciliated 

 pit (c.p.) to central nervous system. Pharyngeal sac (ph.s.); pharynx (ph.); 

 dorsal commissure (d.c.); dorsal ganglion (d.g.); anterior nerve (a.n.); posterior 

 nerve (p.n.). 



