PHYLUM PROTOZOA 



45 



tionable nature of the so-called flagella of certain parasites belonging 

 to the genus spirocheta, many of which are said to have flagella. 

 These so-called flagella are apparently variable structures, for in 



4^; 



Trypanosoma raia?. (After Robertson.) Forms observed in the digestive tract of the leech 

 Pontobdella murlcata. ^-i, mature specimen from blood of skate; B to F, stages in the 

 development of the flagellum from the kinetonucleus, and change in position of the latter in 

 relation to the nucleus. 



many cases as ^'difPuse flagella" they appear not only at the ends of the 

 cell, but at different points about the periphery, and there seems to be 

 no uniformity about their distribution. This is said to be the case in 



