Sharp: Diplodinium ecaudatum 109 



0. purkynjei or that it was overlooked by the observer. Also, as has 

 just been noted, such fibrillar structures as the " Fibrillenschict, " 

 " Querfibrillen, " " Stiitzfibrillen, " "queren Korperfibrillen, " and the 

 "Vereinigung der AuBen stiitzen des inneren kleinen Bogens, " and 

 "des auBeren groBen Bogens" described for 0. purkynjei are lacking in 

 D. ecaudatum. And even if they did occur as figured by the above 

 named author it would be hard to interpret them as being merely sup- 

 porting structures, for according to Braune's figures (pi. 6, figs. 36- 

 43) these "Fibrillen" occur most abundantly, first in those regions 

 of the body which are otherwise well supported by the definite and 

 ample skeletal structures, and secondly in that region which is the 

 most markedly retractile, viz., the oesophageal region. In the former 

 case these fibrillae, in the role of supporting structures, would be super- 

 fluous while in the latter case it would seem as though a contractile 

 function might be more logically assumed for them. 



In regard to the role played by the spines Braune suggests that 

 by means of these, the ciliates which he considers to be normally 

 boring rather than swimming animals, are enabled to keep from slip- 

 ping back while forcing their way through the more solid masses of 

 food. 



Attention has already been called to the fact that in D. ecaudatum 

 the spines, when present, curve in towards the central axis of the 

 body. This seems to be true for 0. purkynjei as well. Such being the 

 case it is difficult to imagine how these spines may be of any assistance 

 whatever in serving to keep the animal from slipping back through the 

 mass of food particles and especially would this be so, if, as Braune 

 points out for 0. purkynjei, that portion of the body just anterior to 

 the spines is greater in diameter than that portion upon which the 

 spines are situated. 



Also in looking at the matter from the viewpoint of evolution, 

 according to Braune's interpretation the presence of these spines being 

 of advantage to the animal, it might be expected that those species or 

 forms so provided with posterior spines would contain the greater 

 number of individuals. Such, however, is not the case, at least this does 

 not hold true for D. ecaudatum. Also it must be noted that many of 

 the forms which are provided with posterior spines are flat, do not 

 habitually rotate about the longitudinal axis and are essentially free 

 swimming and not boring forms. 



Zoological Laboratory, University of California. 

 Transmitted February, 1914. 



