62 University of California Puhlicatio7is in Zoology [Vol. 13 



1. Diplodinium ecaudatum forma ecaudatum Fiorentini 



PI. 3, figs. 1, 2; pi. A, figs. 3-5; pi. 6, figs. 11-19; pi. 7, figs. 20-33. 

 Diplodinium ecaudatum Fiorentini (1889), pp. 15-16, pi. 3, fig. 1. 

 Diplodinium ecaudatum, Eberlein (1895), pp. 263-267, pi. 18, fig. 19. 



Of all the various forms of Diplodinium ecaudatum found in the 

 stomachs of western cattle the most numerous and the simplest morph- 

 ologically is the forma ecaudatum. This form is almost universally 

 present and when once identified may be easily distinguished from 

 all other forms. It is the basis of the following full description, which 

 is applicable to the other forms except only in the region of the pos- 

 terior spines. 



The form of the body is constant (pi. 3, figs. 1, 2), somewhat over 

 twice as long as wide, consistently, circular in cross-section, obliquely 

 rounded off at the anterior and pointedly at the posterior end of the 

 body. In general the body somewhat resembles a rather short, plump 

 banana, the dorsal side being convex and the ventral slightly concave. 

 This resemblance would be still greater if the stem end of the banana, 

 which corresponds in position to the oral opening, be held stationary 

 while the posterior extremity is twisted slightly to the right of the 

 median ventral line. The organs of food-taking and locomotion are 

 situated in the anterior one-fourth of the body, which part is more 

 or less flexible and decidedly contractile. The remaining three-fourths 

 of the body is rigid, friable and comparatively smooth, i.e., free from 

 appendages of any description. The anus is situated at the posterior 

 extremity of the body close to the ventral side. 



The structure of the body is very complicated. It shows plainly 

 (fig. B; pi. 4, figs. 3-5, and pis. 6, 7, figs. 11-33) a cuticle (cut.), 

 an ectoplasm (ect.), and an entoplasm (ent.), with a boundarj'- layer 

 {hd. I.) which separates the ectoplasm from the entoplasm. 



The separate structures which are ectoplasmic in their origin and 

 location are: three skeletal areas with underlying skeletal structures 

 (Z. sk. a., V. sk. a., and r. sk. a.), a macronucleus {mac), a micronucleus 

 (mic), a motor mass (m. m.), motor fibers (d. m. str.), a circum- 

 oesophageal ring (circ. oes. ring), oesophageal retractor strands (oes. 

 retr. str.), a dorsal row of membranelles {d. m.), an adoral row of 

 membranelles {ador. m.), operculum (op.), oral cilia (or. cii), 

 mouth (or.), oesophagus (oes.), caecum (caec), rectum (rect.), anus 

 (an.), and contractile vacuoles (ant. c. v. and post. c. v.). The ento- 

 plasm (ent.) is structureless with the exception of the contained food 

 vacuoles (fd. vac.) and food particles. 



