Anatomical structure of Aspidogaster conchicola. 497 



Across the base of the upper lip lies the transverse neck com- 

 missure (Fig. 1, 3 NC] of the nervous system through the substance of 

 which run some of the before mentioned muscle fibres. In the paren- 

 chyma of the mouth trumpet are nerves, skin glands, and fine vessels 

 of the excretory system which latter is not known to be the case in 

 definitely specialized suckers. 



Pharynx. The pharynx is a distinctly bounded, very compact, 

 muscular organ showing in longitudinal sections an elliptical form — 

 the long diameter in the direction of the intestine — and in trans- 

 verse sections (Fig. 7, 28) a greater depth than breadth. Through 

 its centre in the long axis passes the continuation of the mouth cavity. 

 The muscular walls of the mouth "Trichter" anteriorly as well as those 

 of the intestine posteriorly to it do not join directly on to the inner 

 walls of the pharynx but rather a little round from the margins of 

 its lumen. This gives the pharynx the appearance of jutting slightly 

 into the mouth opening or into the intestine, the former of which 

 often takes place to one third of its length in the living animal. The 

 cuticle follows these slight bends and just in front of the pharynx, in 

 the small dilatation that corresponds to the prepharynx in some other 

 genera, is broken through by the ducts of the circumpharyngeal glands. 

 In sections through the axis of the pharynx (Fig. 1) its two halves 

 curve slightly away from one another in the middle, and towards one 

 another at the ends. The cuticle is very thin at the latter but thick 

 at the former point. Each half shows also a pale border all the way 

 round with a band of deep colored nuclei through its centre. The 

 latter however extends to near the posterior boundary of the pharynx 

 but falls far short of reaching the anterior end. Exceedingly thin 

 transverse sections show the outer pale colored part to be simply 

 muscles. Tolerably thin sections exhibit only a very dense homogeneous 

 mass but sections of 2'/2» 2 and 1 a have given more satisfactory 

 results for this particular organ. Anteriorly the whole section is 

 taken up with circular fibres and with radial fibres but about a quarter 

 of the way backwards the deep colored nuclei appear in the sections 

 and the circular muscles (Fig. 28 ICM, OCM) are crowded into an 

 inner and an outer layer. Voeltzkow mentions inner and outer 

 circular muscles but he does not represent them in his drawing, and 

 in the latter the signature for their position points only to an inner 

 layer which is evidently nothing but the cuticle. The outer layer of 

 circular fibres becomes very dense on the periphery and gives to the 

 pharynx its distinctness of outline. From thin sections the nuclei in 



