No. 7.] OSLER PARASITES IN BLOOD OF FROG. 



407 



No nucleus can be secu. Thou^^h in constant action no change of 

 locality takes place." Fig. 1. 



On looking up the subject I found that the little organism was 

 the Trypanosoma sanguinis which had been described originally 

 by Gruby as an entozoon in the blood of frogs, and by Ray 

 Lankester (not at the time knowing Gruby's observations) as 

 Unfhdina, the type of a new uroup of Infusoria. 



Though a triflhig little object it possesses considerable interest 

 as there is still a doubt concerning its real nature and the move- 

 ment which it displays is unusual, being neither the slow, creep- 

 ing rhizopodal motion, nor yet truly ciliary. Minute protoplasmic 

 organisms usually display one or other of these types of move- 

 ment, but in the object under consideration, there is a peculiar 

 wavy undulation along one margin of the creature together with 

 a lashing vibratile action. Studying the margin under a high 

 power a rapidly succeeding series of waves is seen to pass from 

 one side to the other, increasing in length until at one corner the 

 wave is extended into a lengthened cilium resembling the whip- 

 like flagellum of an infusorian. In the specimens which I 

 examined the undulations always passed in one direction and it 

 appeared as if from the tips of any of the waves the protoplasm 

 could be extended into cilia, though usually only those at one 

 end presented them. It is this latter feature, together with the 

 peculiar wavy character of the motion that gives the creature a 

 special interest and makes it quite an exceptional one among 

 organisms of its class. A fine hair-like extension from the nar- 

 row end was also in constant motion and appeared to vary con- 

 siderably in length, as if it were only a delicate process of the 

 protoplasm, and, unlike a true cilium, capable of elongation or 

 retraction. I kept one under observation for over an hour, during 

 which time the movements kept up, but got slower towards the 

 close. The undulatory motion at last ceased, but the tail-like 



