PLATE 6 



Microphotographs. Diplodinium ecaudatum forma ecaudatum fixed in Schau- 

 dinn 's alcoholic sublimate solution, stained in Heidenhain 's iron-haexmatoxylin. 

 imbedded in paraffin, and sectioned at 5/j.. Nine sections in series. X 600. 



Fig. 11; Tangential section, right side of the anterior one-half of animal 

 nearer to the ventral than to the dorsal side; shows surface markings of the 

 right skeletal area. 



Fig. 12. Note the anterior end of the macronucleus, which lies close to the 

 right dorsal wall of the body. 



Fig. 13. Shows right extremity of dorsal membranelle zone, right side of 

 adoral membranelles, outlines of oesophagus and micronuclens. 



Fig. 14. Note especially the cut ends of the opercular fibers (see op. f., pi. 

 4, fig. 3) and the faint outline of the circumoesophageal ring. 



Fig. 15. Almost a median sagittal section at anterior end, but comes to sur- 

 face of body on right side at posterior end. Shows dorsal neuromotor mass 

 (motorium), oesophageal retractor strands, circumoesophageal ring, boundary 

 layer between ectoplasm and entoplasm, anterior contractile vacuole, posterior 

 limit of macronucleus, and ventral skeletal laminae. 



Fig. 16. Shows food vacuoles in entoplasm, ventral skeletal laminae, faint 

 outline of posterior contractile vacuole between entoplasm and ectoplasm just 

 dorsal to posterior end of macronucleus; and at the same level, near the ventral 

 wall, may be seen the darkly stained granular faecal mass filling the caecum. 



Fig. 17. Note posterior contractile vacuole. 



Fig. 18. Shows rectum and anus. 



Fig. 19. Adoral membranelles and rectum. 



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