3G8 TIMOTHY RICHARDS LEWIS. 



retraction of the flagellum could be observed whilst the organism 

 was in a condition of extreme activity. The specimens in this 

 figure were carefully outlined to scale by means of the camera 

 lucida. 



I am wholly unable to suggest any explanation for the 

 presence of these flagellated parasites in the blood of animals. 

 It will be recollected that they have now been observed in the 

 blood of the horse, camel, and hamster, in addition to that of 

 the rat ; and, further, that they have been found in the blood 

 of two dogs, but whether as the result of intentional inocula- 

 tion or otherwise must for the present be left undecided. As 

 regards the season in which they may be detected, I find that 

 there are entries in my note-book of their having been seen, 

 at one time or another, in the blood of rats in nearly each 

 month of the year. 



For some time I was inclined to think that they might be 

 the spermatozoa of some parasite hidden in the tissues of the 

 animal, a view which strongly forced itself upon me some 

 years ago, in 1878, by having accidentally observed a large 

 number of spermatozoids escaping from the reproductive pore 

 of a fragment of tsenia which I had found while dissecting a 

 rat. The " head " of the taenia was not found, so that the 

 entozoon could not be identified with certainty, but it probably 

 was a portion of Taenia microstoma or some closely allied 

 species. My notes run as follows : — The segments having 

 been placed on a slide spermatozoids are seen to escape from 

 the genital pore of nearly every one of them. Tor a few 

 moments after their escape they presented, with amazing exact- 

 ness, the characters of the spirillar organisms found in the 

 blood of rats, but which were not present in the blood of this 

 particular specimen. It seemed, however, that the water in 

 which the taenia segments were mounted and into which they 

 escaped was not suitable to their preservation. They rapidly 

 underwent changes of form, and almost before half a dozen of 

 them could be sketched disintegrative changes set in, and the 

 previously active flagellated organisms were transformed into 

 quiescent, filamentous shreds. It has not been considered 



