On a Gregarine present in Mid- Gut of Ceratoplrylli. 31 



effect on the subsequent development of T. gambiense ingested within 24 to 

 48 hours after the arsenic blood. 



III. The feeding of flies on arsenic-containing blood immediately after the 

 imbibition of T. gambiense usually prevents further development of the 

 trypanosomes in the fly. In the event of development occurring the strain 

 produced is not arsenic-fast. 



IV. Arsenphenylglycin exerts a prophylactic effect in a monkey against 

 infection with T. gambiense by positive G. palpalis ; this effect varies with 

 the dosage employed, and is considerably greater than when the trypanosomes 

 are introduced by direct inoculation of infected blood. 



On a Gregarine — Steinina rotundata, nov. sp. — Present in the 

 Mid-Gut of Bird-Fleas of the Genus Ceratophyllus. 



By J. H. Ashwokth, D.Sc, and Theodore Rettie, D.Sc, 

 Zoological Department, University of Edinburgh. 



(Communicated by J. C. Ewart, F.E.S. Received September 28, — Read 



December 5, 1912.) 



[Plate 1.] 



The Gregarine described in the following account was first observed by one 

 of us, in autumn, 1909, in the alimentary canal of fleas — Ceratophyllus styx, 

 Rothschild — from a sand-martin's nest.* We have since collected, from 

 several localities in the Scottish Lowlands, numerous larval, pupal, and 

 adult specimens of C. styx, in which we have observed the various phases of 

 development of the parasite. We have also dissected about 500 fleas of 

 other species, in order to determine whether they also harboured the 

 Gregarine which we had found in C. styx. The species examined were 

 C. farreni, Rothsch., from nests of the house-martin ; C. gallinw, Schrank, 

 from nests of the blue-tit, f the blackbird, the thrush, and the robin ; 



* The Rev. J. Waterston had previously reported that he had noticed in a specimen of 

 C. styx, mounted whole, after having been partially cleared in caustic potash, a rounded 

 body of doubtful nature. He kindly obtained for us other examples of C. styx from 

 the locality in which he had collected the specimen referred to. These proved to contain 

 the vegetative phases of the parasite described in this account. 



t Most of the batches of C. gallince examined were from the nests of the blackbird and 

 the thrush, and were found to be either free from Gregarines or infected in very small 

 degree only. But a heavily infected colony was found in the nest of a blue-tit, taken 



