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



than half the width of the body, and its various hooks and 

 highly developed musculature render it a powerful organ 

 of adhesion. It is attached to the posterior end of the body 

 by a comparatively slender and short pedicel, whose down- 

 ward flexure brings the disc to a ventral position where it is 

 partially covered by the body. Three pairs of hooks of 

 different sizes are imbedded in its substance, and protrude 

 upon its under surface. Of these, one pair is relatively 

 very small and not a constant feature in the different species 

 of this genus. Van Beneden (1861) has figured and de- 

 scribed it in E. hippoglossii, and von Linstow (1889) for 

 E. (Phylline) hendorffii, while it is absent in E. bumpusit, 

 judging from Linton's figures and account (1899). Of the 

 remaining pairs of hooks the anterior are the shorter, and 

 are directed forward and outward. The hooks of the third 

 and largest pair, arcuate in form, extend from about the 

 center of the disc to its posterior border, where they emerge 

 with ventrally directed tips. The muscles producing their 

 divergence and approximation are attached to a ridge ex- 

 tending diagonally along their ventral surface. The base 

 of each of the four largest spines is invariably enveloped 

 in one or two large branched cells, and processes from 

 neighboring parenchyma cells also extend to their surface, 

 and apparently spread out to form a thin enveloping sheet, 

 which stains sharply in iron-hsematoxylin. 



The muscle fibers passing from the body through the 

 central part of the pedicel radiate in all directions toward 

 the periphery of the disc. Many of those extending along 

 the more external portions of the stalk follow a similar 

 course, but a considerable number from its right side 

 spread out into the left side of the disc, and those from the 

 left cross over to the right. Circular muscles are also 

 present, especially toward the outer margin of the sucker, 

 and multitudes of fibers penetrate it in a dorsoventral 

 direction. To each spine is attached one or many muscles, 

 some of which are represented in fig. 9. The marginal 

 membrane has its supply of radial and circular fibers; and 

 numerous smaller bands, too numerous and complicated to 



