90 



ON THE CH^TO.SOMATID^, 



row; and tliey He directly under the rows of locomotor seta? 

 thi-oiighout their length (Figs. 27, 29, b.m.). It is probable that 

 they have some relation to the setie, since they are found only in 

 this region; but T cannot trace any direct connection between 

 them. 



Figs. 30, 30a.— 67*. haswe/JI. 

 Fig. 30. — Sagittal, longitudinal section through head; ( x 660). 

 Fig.30a. — Section through mouth-opening; ( x 760). 



The mouth-opening is surrounded by a circular projection, 

 which seems to be protrusible, and bears a circlet of fine teeth 

 (Fig.SOrt). The mouth leads directly into the pharynx, which 

 has very thick, muscular walls, and extends thi'ough the full 

 length of the head. It is constricted in the middle to form 

 anterior and posterior bulbs, of which the posterior is the larger 

 (Fig. 30, a.ph., p.ph.). Both bulbs are slightly larger in the female 

 than in the male, corresponding to a difference in the size of the 

 head. The walls of the anterior pharyngeal bulb consist of a 

 complicated system of muscle-fibres, the arrangement of w^hich 

 is shown in Fig. 30. The passage is narrow, and lined with 

 cuticle, which is thickest towards the mouth-opening. Imme- 

 diately surrounding the passage, there is a mass of finely pig- 

 mented granules; and deeply embedded in the muscle-fibres are 

 numerous, small glands, probably digestive, which open into the 



