ß Art. 8. —S. Goto and Y. Matsudaira : 



the secretion makes them stain paler and distinguishable from the 

 surrounding parenchyma with difficulty. One of the larger groups 

 of prepharyngeal glands taken at random in a sagittal section of 

 the worm measured 40/i in diameter. Next the lining cuticle 

 of the prepharynx lies a layer of circular muscle fibres, followed 

 by one of longitudinal fibres. The prepharyngeal glands lie at a 

 short distance outside these muscle layers. 



The prepharynx is continued posteriorly into an exceedingly 

 muscular pharynx, an ellipsoidal or almost spherical organ meas- 

 uring in three specimens mounted in toto 372 x 312//, 342 x 275 and 

 298 x 298// respectively. Its lumen is flattened dorsoventrally and 

 lined by a comparatively thick cuticle like that of the oral sucker, 

 the direct continuation of that of the prepharynx. Its wall is 

 almost entirely made up of muscle fibres which form numerous 

 concentric bundles with the pharyngeal lumen as the axis. In 

 the thickest part of the pharyngeal wall there are about twenty 

 bundles lying one outside another, and in the median sagittal 

 section of the pharynx, up to some sixty bundles are seen 

 arranged one behind another, the bundles being polygonal owing 

 to mutual pressure and separated from one another by an excee- 

 dingly thin layer of connective tissue. At the two ends of the 

 pharynx there are some especially well developed bundles staining 

 differently from the others, and serving as the sphincters. In the 

 anterior sphincter which is much the stronger one, the bundles are 

 arranged in some six or seven obliquely transverse layers separated 

 from one another by distinct slit-like spaces. The posterior 

 sphincter consists of only three or four similar layers of bundles. 



The muscle fibres of the pharynx appear to be produced for 

 the most part by two pairs of gigantic myoblasts closely applied, 

 two on either side, to the lateral surface of its front half, and sur- 

 rounding the whole organ with a coat of its sarcoplasm. Each one 

 of these gigantic cells is accompanied by two or three smaller cells, 

 probably of the same nature as the principal ones, and a number of 

 very much smaller cells with deeply stained nuclei, which may 

 possibly be nervous in nature. 



