266 CG. CLIFFORD DOBELL. 
(2) Culture of Balantidium entozoon Ehrbg. 
I have been able to watch division and encystment in this 
animal on many occasions, but these have been already 
described by others in more or less detail. The following 
observations are of interest in relation to the species question 
—many different vertebrates harbouring a Balantidium 
resembling B. entozoon. 
I have found that it is possible to cultivate this organism 
in infusions made from the feces of a variety of different 
animals (rats, snakes, etc.). The interest lies in the fact 
that they not only survive, but also remain extraordinarily 
active and multiply by frequent division. They will continue 
to do this for days, so that it is thus possible for these para- 
sites to live and increase also as saprophytes. 
I have found cysts in these cultures, but whether they were 
formed there or originally introduced I cannot say. 
It may be added that Balantidium can also exist in 
certain organic infusions for a considerable time.! 
In conclusion, I gladly take this opportunity of offering my 
warmest thanks to Professor Richard Hertwig for his kind- 
ness to me whilst working in the Zoological Institute in 
Munich. I wish also to thank Dr. Richard Goldschmidt for 
the friendly interest he took in my work whilst there, and for 
his readily offered advice. But my greatest debt of gratitude 
is owing to Professor Adam Sedgwick. What measure of 
success I have achieved is due largely to his inspiration and 
encouragement—without which I should never have under- 
taken these researches. I desire, therefore, to thank him most 
sincerely, as some slight acknowledgment of my indebtedness. 
' Walker has quite recently published an account (‘ Journ. Med. 
Research,’ xviii, 1908) of successful cultivation experiments made by 
him on the flagellates and ciliates in frogs. He states that he has been 
able to cultivate Nyctotherus, Trichomonas, and “ Cercomonas” 
(? Octomitus) on agar media. Neither he nor Strong (‘ Bull. Gov. 
Lab., Manila, 1904), however, has succeeded in cultivating Balan- 
tidium coli. For my own part, I have not been able to cultivate the 
flagellates of frogs on Musgrave and Clegg’s medium for more than a 
few days. 
