144 BIOLOGY OF THE PROTOZOA 



periplasts. This phenomenon has indeed been recorded by some 

 observers, the flagellum, freed from the body, moving off like a 

 spirochete (Klebs, Biitschli, Fischer, etc.). Such observations may 

 or may not be well founded, at any rate accidents of this char- 

 acter are guarded against by the manner of flagellum anchorage in 

 the cell. As described in Chapter III a flagellum is derived from 

 a blepharoplast which may be just below the periplast or deeper 

 in the protoplasm, or it may arise from the nucleus (Fig. 59, p. 108). 

 Its anchorage is further assured by rhizoplasts which sometimes run 

 to the posterior end of the cell as in Herpetomonas or species of 

 Rhizomastix (Fig. 62, p. 116), or which form a branching complex 

 deep in the body substance as in Dimastigamoeba (Fig. 59, p. 108). 

 In the various species of Giardia the basal bodies of the eight 

 flagella are connected by a complete system of rhizoplasts (Fig. 17, 

 p. 37). 



Another type of structure which is regarded by some (e. g., Kofoid) 

 as a modified flagellum is represented by the axostyles or internal 

 motile organoids of the parasitic flagellates. In Trichomonas this 

 appears like a glassy, hyaline curved bar of considerable diameter, 

 extending from the nucleus to the posterior end of the cell where, 

 like a spine, it projects from the periphery (Fig. 77). It is usu- 

 ally interpreted as a supporting axial rod to give rigidity of form 

 to an otherwise soft and variable body (Doflein). Dobell regards 

 it as a remnant of the centrodesmose left in the cell after division 

 of the blepharoplast, a view supported by Hartmann and Chagas 

 (1910) who interpret it as a centrodesmose formed during division 

 of the intranuclear centriole. Martin and Robertson (1909), on the 

 other hand, found that axostyles arise after division quite inde- 

 pendently of the nucleus or of centrodesmose, and regarded them 

 as independent organoids of the cell. Kofoid and his associates 

 discard the assumption that axostyles are supporting or skeletal 

 structures and place them in the category of kinetic elements. 

 They are interpreted as intracellular organoids with a contractile 

 function characteristic of flagella and serve as organs of locomotion 

 in the dense media in which the parasites live and in which the 

 flagella would be ineffective. They are closely connected with the 

 blepharoplasts in all species of Giardia (Fig. 17, p. 37), and are 

 regarded as independent, self-perpetuating organoids which may be 

 the first to divide in the processes of reproduction (Giardia) or the 

 last to divide (Trichomonas). In all cases, according to these ob- 

 servers, but denied by others, the axostyle divides longitudinally 

 throughout its entire length, beginning with divisions of the anterior 

 end in which the blepharoplast may be embedded (Fig. 77). 



In regard to the two opposing points of view as to the function 

 of axostyles the evidence rather supports the interpretation of 

 Kofoid and Swezy (1915). The necessity of a supporting struc- 



