Structure of MagQlona. 441 



The centre superiorly and the sides near the ventral surface 

 inferiorly are marked with brownish pigment. This buccal 

 region^ indeed, may be defined as that lying between the 

 oral aperture in front and the great vertical muscle posteriorl}'^, 

 the latter, moreover, corresponding to the anterior attach- 

 ment of the dorsal wall of the proboscis. It has its ventral 

 margin for the most part open and only completed in the 

 living animal by the approximation of the included proboscis, 

 or the closure of its own walls. The buccal mucous tissue 

 is not extruded to any extent ; that behind is. To the sides 

 of the buccal region are attached various muscular bands, 

 which probably retract the buccal flaps or lips during the 

 extrusion of the proboscis. The anterior buccal tissue, 

 further, is pulled upon by a series of horizontal fibres which 

 come from the anterior part of the roof of the pre-oral 

 chamber in front. At the termination of this region is 

 superiorly a narrow arch of the buccal wall, upon which the 

 dorsal blood-vessel lies, and laterally two wide folds which 

 diminish at their outer and inferior angle, where they are 

 joined by the proboscidian wall. 



The next or pharyngeal region begins at the junction of 

 the proboscidian wall above mentioned, and is further 

 characterized by the presence of a series of longitudinal 

 muscular fibres, which appear outside the basement-tissue of 

 the lateral regions. The outer margin of the glandular 

 layer has laterally a considerable breadth of finely granular 

 tissue, then the chitinous basement-substance, and exteraally 

 the layer of longitudinal fibres, which are entirely lateral in 

 position, i. e. extending from the dorsal to the ventral curve 

 on each side. The canal at this point is much enlarged, 

 while inferiorly the broad glandular lining becomes thinner, 

 and merges into the chitinous coat of the proboscis, Avhich, 

 near the junction, shows an incij)ient glandular layer in- 

 ternally. Further backward bands of strong oblique fibres 

 are attached to the inferior and outer region of the canal — 

 now completed. These muscular bands are evidently the 

 retractors of the organ. Superiorly a narrow retractor is 

 inserted into the wall of the canal at the bend, a larger pair 

 occur laterally, and a similar pair at the ventral border (the 

 specimen had ejected its proboscis but not its pharynx). 

 The latter muscles j)ass transversely outward to be attached 

 to the great mass at the raphe above the longitudinal ventral 

 muscles. The dorsal region of the chamber still has a thin 

 arch of mucous tissue, while it is massive at the sides and 

 ventral region. A slender muscular band from the dorsal 

 raphe (at the side of the dorsal longitudinal) passes inward 



