On Flagellated Protozoa, &c. By Edgar M. Crookshank. 923 



and this could be distinctly traced to be due to the existence of 



a fiagelluin, apparently a posterior flagellum* as the organisms 



seemed generally to move with the thicker end forward ; no flagellum 



could be detected at the opposite end. The greater number of the 



figures in the woodcut (fig. 196) 



are described as representing p IG igg # 



these organisms a few hours after 



the blood had been obtained, 



when their movements are not so 



rapid, and the flagellum becomes 



more recognizable. 



On careful examination the 



plasma which constituted the 



thicker portion of their substance 



was observed to suddenly swell 



out so as to divide the body into 



two parts, as seen in the centre of 



the figure ; at other times two or 



three such constrictions or dilata- „ ., . ,, , , , - 



-, , , n , , ., Parasites m the blood oi rats 



tions were detected, and at other ( a ft er Lewis). 



times the body assumed an arrow 



shape, as depicted at the lower part of the figure. When dried, and 

 stained with a little weak solution of anilin-blue, the body presented 

 a very different appearance. It was found to have contracted irregu- 

 larly, and to manifest a somewhat granular and shreddy appearance, 

 suggestive of a coagulated fibro-albuminous substance. The body 

 portion became flattened towards its middle to double its original 

 width, and both ends almost acutely pointed, while the flagellum 

 was only partly visible. After fixing with osmic acid they 

 measured 0'8-l /m in width, and 20-30 /x in length; the flagellum 

 was about as long as the body, so that the total length of the 

 organism was about 50 /n. Lewis detected these parasites in 

 29 per cent, of the species Mus decumanus and Mus rufescens, but 

 failed to find them in mice. He considered that they had many 

 features in common with motile organisms of vegetable origin, but 

 they appeared to approach much more closely to the Protozoa, more 

 particularly several of the species of Dujardin's Cercomonas. He 

 points out that many, however, believe that these organisms are 



* This observation lei] Kent, who named the organism Herpetomonas Lewisi 

 (' A Manual of Infusoria,' p. 245), to remark that if, as Lewis is inclined to 

 maintain, that organ " propels instead of draws the animalcule through the 

 inhabited serum we have presented a structural and functional feature without 

 parallel among the other representatives of these Protozoa flagelhita, the 

 recognition of which would demand the creation of a distinct generic and family 

 group for the reception of these singular organisms." In his later paper, 

 however, Lewis came to the conclusion that like the generality of flagellated 

 organisms, the rat parasites moved with the lash in front. 



