THE OPALINID CILIATE INFUSORIANS. 



75 



Measurements: A^ of an ordinary individual; B^ of a large indi- 

 vidual with nuclei in active mitosis — 



Measurements, 



Length of body 



Width of body 



Thickness of body 



Length of nucleus 



Width of nucleus 



Diameter of endospherule . 

 Cilia line interval : 



Anterior. . 



Posterior 



This Protoopalina is considerably flattened, its thickness being 

 about one-third of its width, yet its whole appearance shows it to be 

 closeh'^ related to P. longinucleata, P. rhinodermatos and P. regularis. 

 It is spindle-shaped, with broadly rounded anterior end and a narrow 

 posterior end which may be quite slender but is never sharp pointed. 

 Its resemblance to P. longinucleo.ta parallels that of P. intestinalis to 

 P. caudata. The daughter cells show a single dumb-bell nucleus, or 

 the older ones show two daughter nuclei, each spherical or elongated 

 to different degrees, as they develop toward the usual condition as 

 shown in figure 45 a. Fission evidently is consummated while each 

 of the two nuclei is dumb-bell-shaped. Each dumb-bell nucleus be- 

 fore fission is in an anaphase with well-defined macrochromosomes, 

 but I find none clear enough for counting the chromosomes, I judge 

 the number to be 8 but can not be confident. It is certainly not more 

 than 10 or less than 6. With well-preserved material it would be very 

 easy to determine, for there are many nuclei in the most favorable 

 phase for observation of this point. 



The considerable flatening of the body in this species suggests an 

 approach to the condition in the Zelleriellas, soon to be described. 



In this same host are a very few individuals of a species of 

 ZellerieUa. They are very scarce and were not observed until the 

 stained material had faded too much for adequate study. 



PROTOOPALINA SCAPHIOPODOS, new species. 



Type.— United States National Museum Cat. No. 16452. 



Host. — Seaphiopus homhifrons Cope, two infections, one (the type 

 infection) in United States National Museum specimen No. 22265, 47 

 mm. long, from Los Animas, California, July 18, 1892, A. K. Fisher, 

 collector ; the other in United States National Museum specimen No. 

 14554, 50| mm. long, from Black Foot Fork, Snake River, Idaho, 

 Hayden, collector. 



