1919J Kofoid-Swczij: Strchlomastix strix 9 



These myonemes are evidently quite firm fibers, somewhat elastic and 

 more or less rigid. They often stain very deeply especially in dis- 

 integrating individuals (pi. 1, fig. 1). 



' Direction op Toeston 



The direction of torsion of these elements of the nenromotor appa- 

 ratus is not without a deep significance. It is the same as that of the 

 undulating membrane or attached flagellum of Trichomonas. TricJw- 

 mitus, Tcti-atrichomonas and Eutrichomastix (Kofoid and Swezy, 

 1915), other polymastigotes in which torsion finds some structural 

 expression. This same direction of torsion appears in the myonemes 

 of ryrsonympha and Dinenympha (Leidy, 1881). Grassi and San- 

 dias (1893) reverse the direction of Pyrsonympha and of Holomasti- 

 gotes in their figures, while Porter (1897) figures both directions. It 

 is perhaps significant that his figures from life have the reversed direc- 

 tion while those from preparations, and therefore presumably accu- 

 rate, have the normal leiotropic, or to be expected, direction. The 

 reversals figured bj' Grassi and Sandias require confirmation before 

 acceptance. The Ryrsonympha of this contribution (1893) is later 

 designated as S pir ot rich o nymph a by Grassi and Poa (1911) but with- 

 out note of the dififerences in torsion. Zulueta (1915) figures the leio- 

 troi)ic direction in what appears to be Grassi's Spirotrichonympha. 

 While it is quite possible that both leiotropic and dexiotropic genera 

 or species exist, or that functional reversals of torsion occur in the 

 individual it is even more evident that critical observations are essen- 

 tial to establish these diametrically opposed conditions. Pending such 

 investigations the preponderance of the evidence favors the view that 

 the torsion of the more primitive Trichonymphidae is leiotropic, that 

 is from right over to left posteriorly, as it is in Streblomastix. 



This is also the fundamental direction of the girdle and of the 

 encircling transverse flagellum of the Dinoflagellata, and also of the 

 attached collar-forming, ribbon-like flagellum of the Craspedomonadina 

 (Burek, 1909). These facts are suggestive of an extensive and deep- 

 seated leiotropism in the organization of the Mastigophora which finds 

 expression in both externally attached flagella and internal contrac- 

 tile mj'onemes. That it may be conditioned by some equallj' per- 

 vasive stereometric properties of certain compounds of the living 

 substance seems plausible. 



