ZoOL.-VoL. II.] ROBERTSON— ENTOPROCTA. 329 



(^so. V. m.) which fill the space between the ventral wall 

 {v. zv.) and the oesophagus {ces.) are cut more or less 

 obliquely. Close beside the oesophagus in the angle formed 

 by its junction with the stomach {st.) are seen a few mus- 

 cle fibers cut almost transversely. These are the branches 

 of the somatic ventral muscle {br. so. v. ni.). In sections 

 above the plane represented by fig. 5, these transverse 

 fibers become more distinctly grouped together and sepa- 

 rated from the main body of the muscle (fig. 6, br. so. 

 V. m.) They finally fuse with the floor of the atrium (fig. 

 7, c/s. at. Ji. and br. so. v. in.). In succeeding sections 

 the atrial cavity appears and all signs, of muscle bundles 

 disappear. These branches may be called the atrial 

 retractors, for by their contraction the floor of the atrium 

 is drawn downward and the atrial cavity is enlarged. 



All the muscle fibers which branch off from the ventral 

 muscle do not, however, function as atrial retractors. Some 

 of them seem to be in close connection with the genital 

 duct, and perhaps with other organs. Figure 8 represents 

 a section showing an apparent attachment of a muscle bun- 

 dle {ill. g. d.) on each side of the duct leading into the 

 brood-sac. This section is just at the point where the duct 

 {c/s. g: d.) opens into the floor of the atrium {aLJl.) and 

 taken in connection with indications found in other prep- 

 arations, the inference seems to be a valid one that the 

 ventral muscle is connected with the genital ducts in both 

 males and females. 



Sphincter Muscle. — When compared with other genera of 

 Entoprocta, the lophophoral sphincter of Afyosoma has an 

 unusual development. According to Davenport (1893), the 

 sphincter of Urnatella is composed of two or three fibers 

 only. Ehlers gives seven or eight fibers for that of Asco- 

 podaria macropus. An idea of the development which the 

 sphincter attains in this form may be gained from fig. 3 

 {spk. loph.). Here the ends of the fibers appear, cut some- 

 what obliquely, in the deep fold of the lophophore {loph.f.). 

 In frontal section, not represented in the drawings, this 

 sphincter appears as a broad muscular band composed of 

 twenty or thirty muscle fibers arranged in concentric circles. 



