THE OPALTNID CILIATE INFUSORIANS. 139 



M easurements of an ordinary indiviflval. — Length of bodj^ 0.124 

 mm.; ^vidth of body 0.08 mm,; length of posterior spme 0.0054 ± 

 mm. ; diameter of nuclei 0.0038 mm. to 0.0045 mm. ; diameter of endo- 

 sj)herule 0.00155 mm.: cilia interval, anterior 0.0018 mm., middle 

 (».( 10265 mm., posterior 0.00205 mm. 



This Cepedea has the anterior end of the body slightly flattened, 

 as is so usual Avith numerous species. The anterior end of the body 

 is bent to one side, as is true of all cylindrical Opalinids. whether bi- 

 nucleated or multinucleated. The cylindrical species bend their 

 bodies occasionally, as they move about, and an occasional preserved 

 specimen may be found with a straight longitudinal axis, having 

 been caught by the killing fluid and fixed in this temporary condi- 

 tion. Even the flattened forms, whether binucleated or multinu- 

 cleated, show a similar bend in the front end of the longitudinal 

 axis, as may be seen usualh- in the body form and especially in the 

 course of the lines of cilia. 



The posterior end of the bod}- bears a very slender, spine-like tip 

 from Avhich the specific name is taken. The cilia in this species are 

 A ery long, but it is unsafe to give any exact statement of the length 

 from observation of preserved specimens, since the cilia are rarely 

 perfectly preserved. The nuclei are spherical, or very slightly ellip- 

 .soidal, and are few in number, say from 10 to 18. The spheroidal 

 endospherules are rather sparsely distributed through most of the 

 body, but are much more croAvded anteriorly. Crowding of the endo- 

 spherules in the front end of the body is seen in some flattened forms. 

 This species is quite sharply distinct from all others known. 



CEPEDEA DIMmiATA (Stein). 



Opalina dihiidiata Stkix. 



Hosts. — Bona escidenta Limiaeus; Bnfo I'vlgarh Laurenti; Bufo 

 varmhilk Pallas, all from Europe. 



Specimens of this Opalinid have been deposited witli the United 

 States N^ational Museum as Cat. Nos. 1650G to 16509. 



This Avell known Cepedea shows great diversity in size in different 

 infections and as great diversity in the proportions of the bod}^ 

 Some are slender and some very stocky, the most stocky individuals 

 being among the largest of the Opalinidae. These largest, stockiest 

 individuals have been treated by Neresheimer (1907) and Metcalf 

 (1009) as a distinct species, zeUeri. but further study of a large num- 

 ber of infections shoAvs a complete series of intergrading forms. 

 Sometimes in a single infection there wnll be found quite slender 

 forms and very stocky individuals and numerous intorgrades (fig. 

 105). It seems, therefore, that Ave have here, as mProtoopcdina cau- 

 ddta. P. sahunaNs. and a number of other species of all four genera 



