24 BULLETIN OF THE 



of rhabditi-secreting organs in the same region. The slime-secreting 

 glands at the extremities of tlie body are used in Phagocata as a means 

 of attachment, for it is principally by its exti'emities that the worm 

 fastens itself to objects, as can be seen when one attempts to remove it 

 from the side of the aquarium. 



The other glands that are imbedded in the mesenchyma are those 

 which open around the genital orifice. Together with their ducts they 

 resemble in form the parent cells of the rhabditi ; they also react like 

 the glands of the head region with all stains. A portion of one of 

 these glands from an isolation preparation is represented in Plate IV. 

 Figure 41. 



The digestive apparatus of Phagocata is like that of other Triclads, 

 except in regard to the number and arrangement of the pharynges, 

 which form such a striking feature of this species. The form, position, 

 relations, etc. of these pharynges have already (p. 4) been described, 

 and it has also been stated that at the junction of the three main tracts 

 of the intestine there is one pharynx which is larger and more promi- 

 nent than the rest (Plate II. Fig. 20, phy. m.), and that this is the homo- 

 logue of tlie single pharynx of other Triclads. There is no difference in 

 histological structure between this median pharynx and those which con- 

 nect with the lateral tracts. In a cross section of a pharynx (Plate II. 

 Fig. 12) the following layers can be distinguished, beginning from the 

 outside: (1) the fine cilia covering the external surface, (2) the 

 external epithelium, (3) a single layer of longitudinal muscle fibres, 

 (4) a single layer of circular muscles, (5) a wide zone occupied by con- 

 nective-tissue cells and salivary ducts and traversed by radial muscle 

 fibres, (6) a single layer of longitudinal muscle fibres, (7) a broad band 

 of circular muscle fibres, (8) the internal epithelium, and (9) the cilia 

 lining the lumen (compare also the longitudinal section shown in Fig. 16). 

 The external covering of cilia disappears at a region about two thirds 

 of the distance from the free end of the pharynx toward its insertion 

 on the intestine, and the epithelium there loses its smooth appear- 

 ance, becoming wrinkled and creased. The cilia that line the lumen 

 of the pharynx are more restricted in their distribution, and are lost at 

 about one third of the way from the extremity, where the internal 

 epithelium also becomes longitudinally folded, many of the folds pro- 

 jecting far into the lumen of the pharynx (Plate II. Fig. 12, e'th. ?".). In 

 this portion of the epithelium there are many nuclei, whereas in the cili- 

 ated region nuclei cannot be seen. Compare Figures 12 and 16, Figure 12 

 being a cx'oss section which passes through the non-ciliated portion of 



