98 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



cilia line intervals in an average individual from this host are dif- 

 ferent from those of an average individual from L. albilabris^ judg- 

 ing from my material from the two hosts, the intervals for L. caligi- 

 nosus being; cilia line interval, anterior 0.0018 mm., posterior 

 0.00375 mm. A difference so marked is probably significant, but it 

 hardly seems best to name a variety upon the basis of this variable 

 character, especially as the absence of demonstrable nuclei makes 

 the real nature of these forms very doubtful. 



. The material from the two infections of Leptodactylus gracilis is 

 not very well pre ^erved. I have noted no distinctions from the ma- 

 terial in L. alhilahris, except that the individuals from the latter host 

 are for the most part noticeably broader. 



The material from Leptodactylus microtis also is poorly preserved, 

 the nuclei being shrunken, with crinlded membranes, causing them 

 to appear smaller. The Opalinids in both infections are considerably 

 smaller than in L. alhilahris. It is not improbable that study of 

 abundant living material would show specific difference. 



ZELLERIELLA BRASILIENSIS (Pinto). 



Opalina brasiliensis Pinto (1918). 



A specimen of this species has been deposited with the United 

 States National Museum as Cat. No. 16470. 



Host. — Leptodactylus ocellatus (Linnaeus), Pinto (1918) de- 

 scribed this species from Eio de Janeiro, Brazil. My material con- 

 tains one good infection from United States National Museum speci- 

 men No. 22749, 76^ mm. long, from La Plata, Argentina. 



Measurements of a rtiediuTn-sized individual from my material: 

 Length of body 0.13 mm. ; width of body 0.082 mm. ; length of rest- 

 ing nuclei 0.0152 mm. ; width of resting nuclei 0.0109 mm. ; cilia line 

 interval, anterior 0.00195 mm., middle 0.00237 mm., posterior 0.00275 

 mm. Four massive chromosomes. 



The majority of the individuals in my infection are longer and 

 relatively narrower than Zelleriella le^todactyli. Some, however, 

 show the broad form, but none so very broad as the broadest forms 

 of the latter species. The resting nuclei are ovoid. Large individuals 

 with spindle-shaped or dumb-bell-shaped anaphase nuclei are found, 

 also daughter cells with dumb-bell-shaped anaphase nuclei. These 

 conditions indicate that fission usually is consummated while the 

 nuclei are in the dumb-bell anaphase condition, though Pinto de- 

 scribes a still undivided individual with four independent daughter 

 nuclei. One wonders if this individual may have been kept for a time 

 outside the host and so had its completion of the division of the body 

 hindered (see Metcalf, 1909). In a number of the anaphase nuclei, 

 both spindle-shaped and dumb-bell-shaped, four massive chromosomes 



