MORPHOLOGY 55 



known. In such forms, the flagellum appears to arise from the outer 

 edge of the halo. Certain observers such as Woodcock (1906), Min- 

 chin (1912), etc., used the term kinetonucleus. It has since been 

 found that the blepharoplast of certain trypanosomes often gives a 

 positive Feulgen's reaction (Bresslau and Scremin, 1924). 



The blepharoplast and centriole are considered synonymous by 

 some, since prior to the division of nucleus, it divides and initiates 

 the division of the latter. A new flagellum arises from one of the 

 daughter blepharoplasts. While the blepharoplast is inseparably 

 connected with the flagellum and its activity, it is exceedingly small 

 or absent in Trypanosoma equinum and in some strains of T. evansi. 

 Furthermore, this condition may be produced by exposure of normal 

 individuals to certain chemical substances (Jirovec, 1929; Piekarski, 

 1949) or spontaneously (p. 228) without decrease in flagellar activity. 



The flagellum is most frequently inserted near the anterior end 

 of the body and directed forward, its movement pulling the organ- 

 ism forward. Combined with this, there may be a trailing flagellum 

 which is directed posteriorly and serves to steer the course of move- 

 ment or to push the body forward to a certain extent. In a compara- 

 tively small number of flagellates, the flagellum is inserted near the 

 posterior end of the body and would push the body forward by its 

 vibration. Under favorable conditions, flagellates regenerate lost 

 flagella. For example, Peranema trichophorum from which its an- 

 terior flagellum w r as cut off, regenerated a new one in two hours 

 (Chen, 1950). 



In certain parasitic Mastigophora, such as Trypanosoma (Fig. 

 9), Trichomonas, etc., there is a very delicate membrane extending 

 out from the side of the body, a flagellum bordering its outer margin. 

 When this membrane vibrates, it shows a characteristic undulating 

 movement, as will easily be seen in Trypanosoma rotatorium of the 

 frog, and is called the undulating membrane. In many of the dino- 

 flagellates, the transverse flagellum seems to be similarly constructed 

 (Kofoid and Swezy) (Fig. 127, d,f). 



Cilia. The cilia are the organella of locomotion found in the Cilio- 

 phora. They aid in the ingestion of food and serve often as a tactile 

 organella. The cilia are fine and more or less short processes of ecto- 

 plasm and occur in large numbers in the majority of the Holotricha. 

 They may be uniformly long, as in Protociliata, or may be of differ- 

 ent lengths, being longer at the extremities, on certain areas, in 

 peristome or in circumoral areas. Ordinarily the cilia are arranged in 

 longitudinal, oblique, or spiral rows, being inserted either on the 

 ridges or in the furrows. A cilium originates in a kinetosome embedded 



