THE OPALINID CILIATE INFUSOKIANS. 141 



CEPEDEA DIMIDIATA. form ZELLERI (i. e., stocky form). 



See United States National Museum Cat. No. 16508. 



Measurements of a large individual from Rana esculenta. — Length 

 of body 0.32 mm.; width of body 0.184 mm.; diameter of nucleus 

 0.0056 mm. to 0.00765 mm. ; length of endospherule 0.0025 mm. ; 

 width of endospherule 0.002 mm. ; cilia line interval, anterior 0.0012 

 mm., posterior 0.003 mm. 



The posterior ends of the largest individuals are not tapered, but 

 broadly rounded, and are often thrown into rounded ridges. Yet 

 often in these stockiest individuals a slight point may be seen, cor- 

 responding to the posterior point, " spine," or " tail " seen in numer- 

 ous other species. The total number of nuclei in one of the largest 

 of these stocky individuals is about 200. 



INTERMEDIATE FORMS. 



See United States National Museum Cat. No. 16509. 



Intermediate forms completely intergrading between the most 

 slender sort, on the one hand, and the stockiest sort, on the other, are 

 common, and this intergradation is shown not only in size and form 

 of body, but in size of nuclei as well. If this were a rare and inac- 

 cessible species and sa.y only two infections were known, one of 

 slender individuals and the other of the zelleri sort, no one would 

 for a moment consider placing them both in the same species. This 

 illustrates well the necessarily tentative nature of taxonomic con- 

 clusions based upon anything less than a complete series of infec- 

 tions, showing individuals from all phases of the life conditions and 

 the life cycle. An intensive study of a few species from each genus 

 of the Opalinidae is a desideratum, with a view to determining racial 

 differences and structural diversities and their correlation with phy- 

 siological conditions, or with phases of the life cycle. 



CEPEDEA DIMIDIATA ORIENTALIS, new subspecies (flg. 106). 



Type. — ^United States National Museum Cat. No. 16511. 



Host. — Rana nigromacultata Hallowell, two infections, one scant ; 

 the other, the type infection, very abundant, from United States Na- 

 tional Museum specimen No. 23579, 61 mm. long, from Yokohama, 

 Japan, September, 1896, L. Stejneger, collector. 



Measu7'ements of a medium-sized individual. — Length of body 0.18 

 mm. ; width of body 0.045 min. ; diameter of nucleus 0.00375 mm. to 

 0.004 mm.; diameter of endospherule 0.0016 mm. to 0.0018 mm.; 

 cilia line interval, anterior 0.002 mm., posterior 0.0035 mm. 



This Cepedea is similar to C. dimidiata, but in my infections the 

 slender individuals are less slender and the broader individuals more 



