lO CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



dorsally and ventrally (figs. 2 and 3). On the ventral side 

 there is a deep longitudinal groove extending nearly to its 

 center, and from the border of the attachment disc to the 

 left hand end of the external opening of the mouth (fig. 

 3,^; and cross-section, fig. 7,-^) (Notthe "Peristomalrinne" 

 of Wallengren). Just dorsal to this groove in the entoplasm 

 lies a fibre smaller than the one described above, attached 

 to the oral band in the roof of the pharynx, running abo- 

 rally a little to the right of the larger fibre, crossing and 

 extending to the margin of the cup on the left side (figs. 



4' 5> 17. 75./')- _ 



Attachment Disc. — Structurally there may be distin- 

 guished in this disc, which has the form of a shallow thick- 

 walled cup, four distinct layers. The inner, or cuticular 

 layer, bounded at the margin by the inner row of cilia, is 

 finely granular in life, and stains deeply with iron-heema- 

 toxylin. The second layer is homogeneous or possibly very 

 finely granular and does not stain ; this is the only clearly 

 differentiated layer of ectoplasm in Licnophora, and extends 

 only to the outer margin of the cup. The third layer is 

 composed of coarse, deeply staining branches of the axial 

 neck fibre, interwoven and ending abruptly between the 

 basal bodies of the first and second rows of cilia (figs. 4, 

 5 and 75). External to this fibre layer on the left side ter- 

 minates the smaller neck fibre, with its stout branches run- 

 ning to the ventral margin of the cup (fig. 5). The 

 fourth, or outer layer of the cup consists of coarsely 

 alveolar entoplasm continuous with that of the neck and 

 oral disc, and is covered with the general body pellicula. 



On the rounded margin of the cup are four closely set 

 rows of cilia, regularly graded in length from within out- 

 ward (8/^, 16 A*-, 24 /A, 30/i) (figs. 17 and 69). The cilia 

 are usually united into four concentric membranes with 

 more or less deeply fringed edges, but a part of them are 

 often seen separated in the living animal, and in fresh 

 material treated with potassium bichromate or picro-carmine 

 the cilia are always distinct. With a high power (Abbe 



