66 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



of the sexual phases of the Opalinid to the young forms of the host. 

 This might seem to lend some support to Leger and Duboscq's view 

 that P. saturnalis, because of its habitat in a marine fish, is probably 

 a more archaic form than the other species of Opalinidae. But the 

 more natural suggestion seems to be that, the Amphibia being largely 

 terrestrial forms, their Opalinid parasites confine their infection cysts 

 to the aquatic period of the life cycle of the host, and that the 

 encysted forms, hatching in the rectum of the tadpole, being already 

 small, go on with a few further divisions, forming definitive gametes, 

 a much simpler matter at this time than it would be later when the 

 Opalinids had again attained large size. 



Leger and Dubosoq note that the ciliation is always less abundant 

 in the ovoid forms. Certain of them are said gradually to lose their 

 cilia and to become completely naked. Thus in the same infection 

 we find normally motile, broad individuals and completely immobile 

 ones. Similar sparsely ciliated or naked individuals are not known 

 for other species of Opalinids. 



Protoopalina saturnalis has unusually large ectosarc spherules, 

 those in the ovid individuals being especially large. These are said 

 to increase in number with the age of the Opalinid and in the ovoid 

 forms so to enlarge the ectosarc that it almost obliterates the endosarc. 



The resting condition of the nuclei in this species is a peculiar 

 metaphase with the massive chromosomes united into a ring (fig. 

 37, a) more definite than the somewhat similar ring observed in 

 other species, as for example P. intcstinalis. I have not had favor- 

 able material for the study of the details of nuclear structure and 

 mitosis. Leger and Duboscq's figures indicate the presence of both 

 massive chromosomes and granular chromosomes (fig. 37, /), as in 

 other Protoopalinas. The massive chromosomes seem to be about 10 

 in number. The granular chromosomes seem to be more numerous. 

 The authors do not describe or figure any nucleolus. It does not stain 

 with many stains. 



The nuclei in P. satur7ialis come to rest in a telophase of mitosis, 

 and the species should naturally have been described immediately 

 after P. ■fUiformis, since we are arranging our description of species 

 . partly with reference to the mitotic phase in which their nuclei are 

 found, but since P. -filiformis^ P. tenuis^ P. africana and P. xenopodos 

 from a natural series it has seemed best to complete the description 

 of these four species before introducing the description of P. 

 saturnalis. 



PROTOOPAUNA OVOmEA, new species. 



Ty^e.— United States National Museum Cat. No. 16496. 



Host. — Gastrophryne texensis (Gerard) ; one very abundant in- 

 fection in United States National Museum specimen No. 52296, from 

 Brownsville, Texas ; Camp, collector. 



