THE OPALINID CILIATE INFUSOEIANS. 77 



ville, Arizona, August, 1914 ; J. S. Ligon, collector. Eight other toads 

 of this species were opened; six contained no Opalinids, and two con- 

 tained a flat multinucleated form, Opalina ohlanceolata. 



Measurements of an average individual. — Length of body 0.195 

 mm. ; width of body 0.05 mm. ; length of nucleus 0.037 mm. ; width 

 of nucleus 0.0113 mm.; endospherules not clearly seen; cilia line 



P"IG. 47. PKOTOOPALINA HAMMONDII, X 460 DIAMETERS. 



interval, anterior 0.00188 mm., middle 0.00375 mm., posterior 0.00375 

 mm. Six massive chromosomes. 



This species, in my infections, is a third smaller than P. scaphio- 

 podos. but resembles it \Q,vy closely in form. Its nuclei are closely 

 similar, except that they have six instead of eight massive chromo- 

 somes. 



PROTOOPALINA MITQTICA (Metcalf). 



Opalina mitotica Metcalf (1912.) 



Type. — Now deposited in United States National Museum as Cat. 

 No. 16454. 



Host. — Amby stoma tigrinu/m (Green). These Opalinids were 

 found by J. H. Powers, late in the fall, in Lincoln, Nebraska, in 

 numerous young Anibystom,a of this species, which had been kept in 

 iiquaria for a month or more. 



Mcaswrcmerds. — Length of body 0.3 mm.; width of body 0.0374 

 mm. : length of nucleus 0.0348 mm, ; width of nucleus 0.012 mm. ; 

 diameter of the disk-shaped endospherules 0.0037 mm. ; thickness of 

 same 0.001 mm. ; cilia line interval, anterior 0.0025 mm., posterior 

 <1003 mm. Ten massive chromosomes. 



This Protoopalina is very similar to P. scaphiopodos in size and 

 form of botli body and nuclei. Its massive chromosomes, however, are 

 10 in number. In the ordinai-y nuclei they are more angular and less 

 elongated than the chromosomes of P. scaphiopodos or P. hammondii, 

 indicating, apparently, a transition from anaphase to telophase con- 

 dition. This was the first Opalinid described in which there was 

 observed the habit of bringing the nuclei to rest in a mid-mitotic 

 condition rather than in the reticulate condition usual in the resting 



