64 University of California Publications in Zoology [Vol. 13 



Alitor in der iiber die Infusorien des Wiederkauermagens handelden, 



mir zugangliehen Litteratur etwas bemerkt hat Nach meinen 



Beobachtiingen stellt dasselbe einen Stiitzapparat fiir den Schlund 

 dar. " And again in his paper of 1900 he adds that he has also found a 

 corresponding structure in Entodinium rostratum Fiorentini. But 

 in neither of these papers does Giinther (1899 and 1900) make men- 

 tion of a surface differentiation of the cuticle corresponding to the 

 underlying ectoplasmic structures ("Stiitzapparat"). As a matter of 

 fact these peculiar structures {sk. lam., pi. 4, figs. 3, 4, 5) with their 

 overlying areas {I. sk. a., v. sk. a., and r. sk. a., pi. 3, figs. 1, 2) which 

 I have found in Diplodinium, and which appear to be skeletal in 

 function, and are so designated in this paper, are so different from 

 anything heretofore mentioned that a rather complete description is 

 deemed in order. 



Skeletal Areas. — The skeletal structures proper will be described 

 in connection with the ectoplasm. The corresponding areas of cuticle, 

 which will be designated as a left skeletal area, a ventral skeletal area, 

 and a right skeletal area, show well-defined boundaries. 



The left skeletal area (1. sk. a., pi. 3, fig. 2), the smallest of the 

 three, is triangular in shape with its base anteriorly marked off by 

 a line drawn horizontally from the left extremity of the dorsal mem- 

 branelle zone {d. m. z., pi. 3, fig. 2) to meet the adoral membranelle 

 zone [ador. m. z., pi. 3, fig. 2) near its left extremity, and its apex 

 extending obliquely posteriorly and toward the right to end on the 

 ventral side about midway between mouth and anus. The ventral 

 skeletal area {v. sk. a., pi. 3, figs. 1, 2), the largest of the three areas, 

 is rectangular in shape and extends from the base of the outer adoral 

 lip (pi. 3, figs. 1, 2) somewhat obliquely towards the posterior end and 

 slightly towards the right to blend with the right skeletal area just 

 anterior to the middle of the body. The right skeletal area {r. sk. a., 

 pi. 3, fig. 1), intermediate in size, also somewhat triangular in shape, 

 with base marked off by a line extending from the right extremity 

 of the dorsal membranelle zone to the dorsal side of the base of the 

 outer adoral lip, and apex extending posteriorly, blends with the 

 ventral skeletal area just anterior to the middle of the body. The 

 two areas then extend posteriorly to terminate rather indistinctly 

 at about the last fourth of the body. The relation of skeletal areas to 

 underlying skeletal structures may be seen best by a consideration of 

 plate 4, figure 4, and plate 7, figures 23-29. The cuticle over these 

 areas is more transparent than elsewhere and through it may be seen 



