THE TREMATODA 



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3 



FIG. XIX. 



1. Transverse section of the ventral sucker and neighbouring part of the body of 

 Distomum hepaticum (orig.). , cuticle ; b, outer transverse muscles, which appear to become 

 continuous around the margin with the inner transverse muscle (h) ; c, radial muscles passing 

 through the whole depth of the sucker ; the bundles of muscle fibres are separated by con- 

 nective tissue represented by dots, in which the large myoblasts (d) are embedded, two of 

 which are shown in the section ; ee, circular muscle fibres, chiefly developed around the 

 margin of the sucker ; /, retractor muscles of the sucker, derived from the dorso-ventral body 

 muscles, which serve to move the sucker as a whole ; g, the internal limiting cuticular sheath 

 of the sucker ; h, the internal transverse muscles of the sucker. 



2. Diagrammatic transverse section through the body wall of a Trematode, composed 

 from descriptions and figures of various authors, and from my own observations, a, the cuticle, 

 vertically striped in its deeper portions ; b, spinelet, occurring in Malacocotylea ; c, sub- 

 cuticular protoplasmic layer joining the upper ends of the epidermal cells (c'), which have 

 been separated from one another by the upgrowth of the mesoblastic tissues. Below this layer 

 is the basement membrane (d) ; e, circular layer of muscles ; /, longitudinal layer of muscles ; 

 g, branched parenchymal cell, the processes of which subdivide and anastomose to form a net- 

 work^) of fine threads invading the muscular and epidermal layers; h, a "vesicular cell," 

 such as occurs in various Trematodes, in greater or less abundance. 



3. Longitudinal section through the posterior sucker and the hinder end of the body 

 of Tristomum ovale (from Goto), a, sucker, not delimited internally from the tissues of the 

 body (6) ; c, longitudinal muscles of the body passing into the sucker and spreading out therein ; 

 d, radial or dorso-ventral muscles, between the bundles are groups of "sticking glands" not 

 indicated ; e, transverse muscles ; /, marginal membrane. 



4. Longitudinal section through one of the eight suckers of Dactylocotyle denticidatiim, 

 Olss. (from Cerfontaine), which is parasitic on the gill filaments of Gadus carbonarhis. The 

 sucker is " valvate " and armed ; the figure shows the armature, but not the muscular sucker ; 

 and three branchial filaments are clasped, a, b, chitinoid armature ; c, gill filaments ; d, divari- 

 cator muscles, serving to open the valves ; e, occlusor muscles. 



5. The chitinoid skeleton (armature) of a sucker of Dididophora elongata ; the skeleton 

 consists of three pairs of pieces (cde) set round the margin of the sucker, and two transven 

 unpaired pieces (ab). 



C. Longitudinal section through one of the eight suckers of Cycl. sessilis, Goto, from 

 the oral cavity of Chaerops japonicus. The sucker is limited internally (k), but the intrinsic 

 muscles are subdivided by the skeleton, ace (cf. Fig. 5), to which, as well as to the sucker 

 itself, retractor and other muscles (hj) are inserted for its movement ; g, the marginal membrane. 



