TTHE opalinid ciliate infusorians. 



After this paper was mostly written the American Museum ot 

 Natural History, in New York City, most kindly offered, through 

 its director. Dr. F. A. Lucas, and its curator of reptiles and amphibia, 

 Mary C. Dickerson, to send me material of Pipa from South Amer- 

 ica and of Xenopus from Africa. This material was especially wel- 

 come because the United States National Museum specimens of these 

 genera had proven to be uninfected and the parasites of these mem- 

 bers of the family Pipidae are of peculiar interest, first, because it 

 is the most archaic family of the Anura, and second, because of the 

 geographical distribution of the family, the Pipinae living in 

 northeastern South America and the Xenopod- 

 inae in Africa. I wish to express most cor- 

 dially my thanks for this material. 



The major interest in this paper is associated 

 with data from the material gathered from the 

 collections of the United States National Mu- 

 seum; and 1 can not adequately express my 

 thanks to the authorities of the museum, and 

 especially to Doctor Stejneger, for the privilege 

 of taking Opalinids from the Anura in their 

 collections and for the facilities they gave me 

 for the work for three months during the win- 

 ter of 1916-17. Such liberal conception of the 

 use of museum facilities, and especially mu- 

 seirni material, is far from universal. The au- 

 thor sincerely hopes that his fortunate finds 

 will be held to justify this liberality. Should 

 any other museums with extensive material undertake to have this 

 searched for intestinal parasites, the author will gladly send them for 

 comparison specimens of the species described in this paper, so far as 

 his material will allow.^ 



Opalinids live in the rudimentary caecal portion of the rectum of 

 their Anuran * hosts (fig. 1). When they are exceedingly numerous 

 they may be found in the whole upper portion of the rectum. Only 

 in a few instances have I found Opalinids in the small intestine of 

 the Anuran host, and in several of these cases the host was evidently 

 in abnormal condition, the intestinal tract showing inflammation. 

 In studving material from living hosts, it is easiest to remove the 

 whole rectum to a small dish ("Syracuse solid watch glass") and, 

 opening carefully the caecal region, to collect with a pipette, or as 



Fig. 1. — Side view of kec- 

 tdm op frog i c, rudi- 

 MENTARY CAECUM ; m, 



DORSAL MESENTERY ; r, 

 RECTUM ; S, i, SMALL IN- 

 TESTINE. 



• '■^ See Section 10. p. 448, in which is given a Ust of the museums and laboratories in 

 which the author is depositing series of paratype slides. 



* In the mucli rarer infections of Urodeles they appear throughout the posterior third 

 or half of the intestines, and the same is true of Protoopalina satunialis m the marine 

 fish Box hoops. 



