THE OPALINID CILIATE INFUSORIANS. 239 



OPALINA ROTUNDA, new species. 



Type. — United States National Museum Cat. No. 16602. 



Host. — Rana enjthraea (Schlegel) , one scant infection from United 

 States National Museum frog No. 53518, 28 mm. long, from Ok 

 Yam, Siamese Cambodia, January, 1915 ; C. Boden Kloss collector. 



Measurements of a large, hroad individual. — Length of body 0.09 

 mm.; width of body 0.1 mm.; thiclmess of body, anterior 0.022 mm., 

 middle 0.026 mm., posterior 0.028 mm. ; length and width of nuclei, 

 first 0.005 mm. by 0.005 mm., second 0.0055 mm. by 0.0055 mm., third 

 0.0055 mm. by 0.0035 mm., fourth 0.0057 mm. by 0.0045 mm!, fifth 

 0.006 mm. by 0.005 mm., sixth 0.0066 mm. by 0.0047 mm., seventh 

 0.008 mm. by 0.0057 mm. ; diameter of endospherule .002 mm. : cilia 

 line interval, anterior 0.00172 mm., middle 0.0025 mm., posterior 

 0.002:) mm. 



Fig. i;14. — Opalina rotunda : a is magxified 460 diameters, and all the lines op 



CILIA ON THE UPPER SURFACE ARE SHOWN ; h, A GROUP OF CELLS, MAGNIFIED 117 DIAM- 

 ETERS. 



This little OpaJina is usually very broad, but some narrower forms 

 are seen. The body is thinnest in front and thickest behind. Its 

 nuclei are for the most part ellipsoidal, but some are spherical. As 

 the spherical ones are rather small, probably they are daughter 

 nuclei not yet elongated into the typical resting condition. The 

 species seems sharply distinct from any other. 



OPALINA CINCTA Collin (1913). 



Host.—Bufo hufo (Linnaeus) \Bujo vulgaris Laurenti], from 

 Viarmes, France. As I have had no material of this species, I quote 

 from Collin's description. 



Measurements, taken from CoUhi's /t^wre.— Length of body 0.141 

 mm. ; width of body 0.104 mm. ; diameter of spherical nuclei 0.01 mm., 

 length of anaphase nuclei 0.0194 mm. ; width of same 0.0094 mm. 



In this orbicular Opalina the ectosarc is very wide around the 

 whole contour of the body. The nuclei are very large, larger even 

 than in O. ranarv.m form cinctoidea, and almost all are in division. 

 This last is a noteworthy feature in a multinucleated Opalinid. We 

 have seen it in many of the binucleated species, both Protoopalinas 



