924 Transactions of the Society. 



zoospores and not animalcules. To him they also seemed to be not 

 unlike the flagellated parasite described by Biitschli.* 



The latter observer, I find, detected flagellated organisms 

 (Leptomonas t Biitschlii) in the intestinal canal of a free nematode 

 I'Trilobus gracilis). They too form stellate colonies, as I have 

 photographed from a stained preparation of the Surra parasite, 

 owing to their being attached by their non-flagellated ends. 

 When detached from these colonies they presented a somewhat 

 spindle-shaped body about 11 fj, in length, with a somewhat 

 thick flagelluni about double this in length, so that the 

 total length of the protozoon would be 33 fi, or as Lewis states, 

 about half the length of the flagellated organism in the rat's blood. 

 Near the base of the flagellum Biitschli s protozoon presented a 

 contractile vacuole, but Lewis was unable to detect any such 

 vacuole in the rat haematozoa. 



In conclusion Lewis observed that, very probably, these organ- 

 isms corresponded with the vermicules observed by I)r. Goss in the 

 blood of a field mouse, and he also mentions that M. Chaussat found 

 minute nematodes in the blood of a black rat. 



Before passing on to compare my observations with those of 

 Lewis, I may here state that in the autumn of 1879, Wittich X 

 discovered in the blood of hamsters, whip-like bodies with lively 

 movements. They resembled frog's spermatozoa, possessing a 

 thick portion continued into a long lash-like thread. Wittich con- 

 sidered them identical with the organisms described by Lewis, and 

 they also were observed in apparently healthy animals. Koch 

 later § met with the same organisms. 



I now pass on to describe my own observations upon the 

 common brown rat in England. Like Lewis 1 found that the 

 blood appeared to quiver with life, and that the parasites were 

 extremely difficult to examine until their movement was arrested 

 for a moment or they became imprisoned in the serum area3. 

 After examining with various powers, from a 1/5 dry to a 1/25 

 oil-immersion of Powell and Lealand, I came to the following con- 

 clusions : — That they are polymorphic, presenting for the most 

 part slightly tapering bodies which terminate at one end in a 

 stiff, immotile, acutely-pointed flexible filament or spine-like 

 process, and at the opposite end are provided with a long 

 flagellum, while longitudinally attached a delicate undulating fin- 

 like membrane can be traced, which starts from the base of the 

 posterior filament, and becomes directly continuous with the 

 flagellum (fig. 197). 



* " Researches on the flagellated Infusoria and allied organisms," Zeitschr. f. 

 Wiss. Zool., xxx., and Quart. Journ. Micr. Sci., lxxiii pp. 63-103, pi. VI. fig. 5. 

 f Kent, ' A Manual of the Infusoria,' p. 243. 



J " Spirillen im Blut von Hamstern," Centralbl. f. Med. Wiss., 1881, No. 4. 

 § Mitteilungen aus der Kaiserlich. Gesundh., 1881, p. 8. 



