38 DISCOPHOR^. Part HI. 



to have an individuality of its own; one, two, or three sides may collapse, and 

 leave the others undisturbed {Fifj. 19 a), or all four together fold longitudinally 

 {Fig. 15) and inwardly, so as to form a cruciform passage {d) to the digestive 

 cavity. The corners of the mouth are very active in their versatile contortions 

 and extensions, forcibly bringing to mind the movements of the prolongations of 

 Rhizopods, especially the Difflugia and Amoeba forms. 



The digestive cavity (PI. X^. Fkjs. 19, 20, and 28 h) occupies about two thirds 

 of the transverse diameter of the disk, and in shape may be compared to a double 

 convex lens, the thickness corresponding to the axis of the body. The radiating 

 chymiferous canals {c d) of the oculiferous lobes extend their course to the very 

 base of the ocular peduncles {Fi(js. 19, 20, 28, 31, and 33 h), but change somewhat 

 in form; the basal part is equal to one third of the breadth of the lobe, the 

 portion corresponding to the mid-region of this lobe {Fig. 31 d) is slightly nar- 

 rowed, and then, at the base of the ocular peduncle {li), suddenly broadening ((/•'), 

 occupies one third more space than at its base. The chymiferous tubes, which go 

 to the tentaculiferous edge, are also broadened near the end {Figs. 19, 28, and 

 31 e), but suddenly narrow to the breadth of the basal part. The depth of 

 these canals has also changed, and, with this, the form of the transverse section, 

 as may readily be seen by looking at a foreshortened view {Fig. 33 c) of an 

 oculiferous lobe, when the pointed, roof-like dorsal side becomes apparent. The 

 lloor of these canals is concave, but each half of the roof is convex. The sharply 

 defined, usually irregular line {Figs. 19 and 31 d f) which runs along the middle 

 of the upper side of each canal indicates the fold of the internal wall at the 

 apex of the roof-like ceiling, and the smaller branches which project obliquely out- 

 ward and downward from the main line are smaller folds in the slope of the 

 roof In the ocuUferous lobes {Fig. 31), the ridge ((/) of the roof forks, and one 

 branch {d^) goes to each half of the T-like exjjansion at the end of the chymiferous 

 canal. 



The digitate appendages (PI. XP. Fig. 18 c, Figs. 19 and 28 g) of the repro- 

 ductive organs have doubled their number. Upon close examination Ave find that 

 they are hollow, closed, deep pouches or tubes, which open downward into the 

 space between the outer and inner walls (PI. XP. Fig. 21), and are composed of 

 a single wall («), which is in direct continuance with the lower, inner wall {(i) 

 of the digestive cavity. It is rather remarkable, that they are endowed with 

 numerous lasso-cells; but as we have at times seen them protruded from the mouth 

 of the proboscis, it may be that they have an office to perform exterior to the 

 digestive cavity. 



The ocular peduncles (PI. XP. Figs. 19, 28, 31, 33, and 34 h) are cylindrical for 

 half of their outer end {Fig. 34 h h^), and at the basal half {h^ h^) broadly conical 



