476 



WM. A. KErXER AND "\V. J. SCOTT 



zapfen' of Gyratrix (c). A highly refractive third zone of 

 muscles lies between the end cone and the muscle spindle of the 

 base of the pharynx, {b). Thus, in this series of Prorhj^nchus 

 which has no proboscis there is a highly muscular pharynx 

 whose histology is as complex, if not more so, than that of the 

 complex proboscis of a Gyratricid. 



Text fig. A Drawing of dorsal aspect of Prorhynchus applanatus. DG, 

 dorsal ganglion; E, eye; P, pharynx; a, b, and c, the three regions of the muscu- 

 lar pharynx. X 75. 



The functioning of this most complex pharynx of the Rhab- 

 docoela is not supplemented for a long period during the life of 

 each individual by a penis which might act as an organ of defense. 

 Animals are frequently found with the ovaries present. Sel- 

 dom are the male genitalia encountered. These appear for but 

 a brief period in the history of the individual. Therefore, the 



