4 Art. 8.- S. Goto and Y. Matsudaira : 



circular and irregularly meridional. The radial fibres which are very 

 well developed traverse the whole thickness of the wall and are 

 inserted at their ends to the cuticle and the external limiting 

 membrane respectively and form more or less distinct bundles. 

 The circular fibres form a layer of some thickness, about 8//, immedi- 

 ately adjoining the lining cuticle, and form bundles separated from 

 one another by those of the radial fibres. They are especially well 

 developed at the front and hind ends of the acetabulum and are 

 reinforced at the former by some additional bundles lying more 

 outwardly in the same plane with the irregularly meridional fibres 

 directly to be described, and form together a sphincter. The 

 layer of irregularly meridional fibres lies just under the external 

 limiting membrane, the fibres decussating irregularly with one 

 another but running parallel to the limiting membrane and in some 

 places meridionally. In the connective tissue of the acetabulum, 

 between the bundles of the radial fibres and the layers of circular 

 and irregularly meridional fibres, lie numerous, deeply stained 

 unicellular glands, which open by long ducts mostly along the 

 margin of the acetabulum, but in smaller numbers also on its 

 whole inner surface. The ducts that open on the front margin of 

 the acetabulum pass between the bundles of the circular and the 

 irregularly meridional fibres mentioned above. In the parenchyma 

 surrounding the acetabulum there are groups of unicellular glands 

 which open on the body surface around the acetabular orifice. 



The oral sucker is followed by the prepharynx, which is re- 

 markable by its length and close windings and the structure of its 

 inner lining. If straightened out it would be nearly as long as 3 

 mm., therefore about equal to the body length, but is wound upon 

 itself so that in the natural state it occupies only one-fourth as 

 much linear space. Taken as a whole, it may be said to describe 

 two U's open in front, a smaller one inside a larger; the smaller, 

 anterior and ventral, connected with the oral sucker by the 

 front end of its left arm; the larger, posterior and dorsal, connected 

 with the pharynx by the front end of its left arm, and the right 

 arm of the smaller U continued to the right arm of the larger one 

 (figs. 1, 3). The canal measures about 70/* from side to side, and 



