PLATE 7 



Figs. 20-32. Cross-sections of Diplodinium ecaudatum, fixed in Zenker's 

 fluid, stained in modified Mallory's connective tissue stain, embedded in paraf- 

 fin, and sectioned at 6 microns. Microphotographs. X 750. This series (series 

 A-2-c-l) contains twenty sections, of which only eleven are here reproduced, 

 figure 20 being the second section of the series and figure 32 the nineteenth 

 section; figures 29 and 30 are taken from a second series (series A-2-C-2). 

 Section 1, although clear on the slide, could not be satisfactorily photographed. 



Fig. 20. Section 2 of series A-2-c-l is cut somewhat obliquely with refer- 

 ence to the longitudinal axis of the body, but in an almost exact transverse 

 plane with reference to the oral and adoral region of the animal. Note the 

 oral opening (cf. fig. A) and adoral membranelles. 



Fig. 21. Section 3, series A-2-c-l. Although cut more deeply than figure 

 20, this section shows the oral and adoral arrangement to even better advan- 

 tage (cf. figs. A, C). 



Pig. 22. Shows the left extremity of the adoral row of membranelles. 



Figs. 23-25. Sections 5-7, series A-2-c-l. Taken through the dorsal mem- 

 branelle zone. Compare with plate 4, figure 4. Note especially the darkly 

 stained oesophageal fibers (cf. oes. f., pi. 4, fig. 4) and the dorsal motor strand 

 (cf. d. TO. sir., pi. 4, fig. 4). 



Fig. 26. Note outer and inner dorsal lips (cf. o. d. lip and i. d. lip, pi. 4, 

 tig. 4) and the three skeletal regions. 



Fig. 27. Section 9, series A-2-c-l. Shows anterior end of macronucleus 

 and areolar, contractile vacuole region (cf. c. v. r., pi. 4, fig. 3). 



Fig. 28. Shows especially well the anterior contractile vacuole. 



Fig. 29. Section 11, series A-2-C-2. This series is from a somewhat larger 

 animal and was taken from an ox which had not been fed for some 18 hours. 

 Note that there are no food vacuoles in the entoplasm. Shows macronucleus 

 and micronucleus and proximity of oesophageal wall to the micronucleus (cf. 

 pi. 4, fig. 4). 



Fig. 30. Section 15, series A-2-C-2. Shows posterior contractile vacuole. 



Fig. 31. Section 17, series A-2-c-l. Through posterior extremity of macro- 

 nucleus and posterior contractile vacuole, and through junction of rectum and 

 caecum. 



Fig. 32. Section 19, series A-2-c-l. Shows rectum enlarging into anal slit. 



Fig. 33. Paramedian section of D. ecaudatum forma ecaudatum, just to right 

 of median sagittal plane. Microphotograph of 15 y. section. X 600. (Cf. pi. 4, 

 fig. 3.) 



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