92 University of California Publications in Zoology [VOL. 13 



3. Diplodinium ecaudatum forma bicaudatum forma nova 



PI. 5, fig. 7 



This is the least abundant form of the species. It is characterized 

 by the presence of a secondary spine (sp. 2, pi. 5, fig. 7) or tail-like 

 continuation of the posterior extremity of the body. The base of this 

 spine is located to the left of the median plane and close to the dorsal 

 side of the body and the spine itself curves ventrally and inward. This 

 secondary spine varies in size from a mere nodule situated just to the 

 right and dorsal to the anal opening up to a spine one-half to two- 

 thirds the size of the primary spine. The morphology of the secondary 

 spine is identical with that of the ventral or primary spine. The pos- 

 session of a secondary spine in nowise affects the position or mor- 

 phology of the ventral or primary spine, but does, when large, affect 

 to some extent the shape of the dorsal portion of the posterior end of 

 the body. When more than one spine is present the posterior end of 

 the body is relatively enlarged for their accommodation and the body 

 appears more nearly cylindrical. These changes in size relationships 

 may be seen by a comparison of figures 6-10, plate 5. In no other 

 way does forma bicaudatum differ from forma caudatum. Dimensions 

 of this form are given on page 95. 



4. Diplodinium ecaudatum forma tricaudatum forma nova 



PI. 5, fig. 8 



This also a relatively rare form, is distinguished by the presence of 

 a third spine. This third or tertiary spine (sp. 3, pi. 5, fig. 8) is 

 located rather to the right of the median plane and, as in the case of 

 the secondary spine, curves ventrally and inward. The tertiary spine 

 may also be present as a mere nodule situated rather close to the right 

 extremity of the anal slit or may be quite as large as the secondary 

 spine. I have never found either the secondary or the tertiary spine 

 to be as large as the primary one, although the secondary and tertiary 

 sometimes equal each other in size. The secondary spine, however, is 

 generally the larger of the two. 



The presence of this third spine (sp. 3} does not in any way affect 

 the primary (sp. 1) and secondary spines (sp. 2}. The posterior end of 

 the body, however, is necessarily a little larger. 



Dimensions of this form are given on page 95. 



