TYPE PROSOP7GIA. 257 



within the vestibule, and the rirn of the cup can be closed 

 over them, owing to the presence in it of a circular band of 

 muscle-fibres. 



The entire body is covered by a delicate cuticular ectocyst 

 similar to the cuticle of the Annelids, below which is the 

 ectoderm containing numerous gland-cells, as well as scat- 

 tered sensory hair-bearing cells which, however, have not been 

 found to exist in some genera (Ascopodaria). Scattered mus- 

 cular fibres occur in the body-wall, but they do not as a rule 

 reach an extensive development. 



The co3lom is of very slight extent and in Loxosoma is re- 

 placed by a gelatinous matrix enclosing branching cells and 

 muscle-fibres and recalling the parenchyma of the Turbel- 

 laria. Imbedded in this parenchyma is the U-shaped diges- 

 tive tract, beginning with the mouth situated in the vestibule 

 and overhung by a well-marked epistome. The mouth leads 

 into a narrow oesophagus lined by ciliated columnar cells, 

 and opening below into a saclike stomach (Fig. 114, s) 

 which forms the lower transverse portion of the U. The 

 cells of its anterior (vestibular) wall (?) are large and destitute 

 of cilia, and contain numerous granules, on which account 

 they have been termed " liver-cells." The intestine forms 

 the ascending limb of the U, and like the oesophagus is cili- 

 ated, opening into the vestibule at the summit of a well- 

 marked papilla. 



The nerve-ganglion lies below the floor of the vestibule 

 between the epistome and the anal papilla and is a single 

 dumb-bell-shaped structure from which from one to three 

 nerves arise on each side, branching to be distributed to the 

 tentacles and muscles of the body. 



A single pair of nephridia occurs, opening into the vesti- 

 bule, and each is composed of a number of perforated cells, 

 the lumen being ciliated. It is doubtful whether a flame-cell 

 occurs at the inner extremity as in the Annelid head-kidneys, 

 which otherwise they resemble. Most of the Endoprocta seem 

 to be bisexual, though Pedicellina is perhaps hermaphrodite. 

 The reproductive organs arise from the mesoderm of the body- 

 wall, forming masses projecting into the parenchyma, and are 

 provided with special ducts which either remain independent 



