PROTOZOA 



protoplasm it has a honeycombed or alveolate structure, but in 

 this case tlie alveoli are permanent in their arrangement and 

 position. Kows of these alveoli run under tlie surface ; and the 

 cilia are given off from their nodal points where the vertical 

 walls of several unite, and wherein the basal granule or blepharo- 

 plast is contained. Longitudinal tlireads running along the 

 inner walls of the alveoli of the superficial layer are differen- 

 tiated into muscular fibrils or " myonemes," to which structures 



.^ 



Fig. .'iO.— Eutosare of Ciliata. «-/', from Stentor coeruleiis ; g, Holophrya discolor, a. 

 Transverse section, showing cilia, pellicle, canals, and myonemes ; b, surface view 

 below pellicle, showing myonemes alternating with blue granular streaks ; c, jiiore 

 superticial view, showing rows of cilia adjacent to myonemes ; d, myoneme, highly 

 magnihed, showing longitudinal and transverse striation ; e, two rows of cilia ; /, g, 

 optical sections of ectosarc, showing pellicle, alveolar layer (a), myonemes (m), and 

 canals in ectosarc. (Fi'om Calkins, after Metschnikoff, Biitschli, and John.sou.) 



so many owe their marked longitudinal striation on the one 

 hand, and their power of sudden contraction on tlie other. The 

 appearance of transverse striation may be either due to transverse 

 myonemes, or produced by the folds into which the contraction 

 of longitudinal fibrils habitually wrinkles the pellicles, when it is 

 fairly dense (Peritrichaceae) ; circular muscular fibrils, however, 

 undoubtedly exist in the peristomial collar of this group. 

 Embedded in the ectosarc are often found trichocysts/ analogous 



^ See jMitrojiliaiiow " Sur les Tnciiocystes . . . du Paravioccium," Arch. 

 I'rotist. V. 1904, p. 78. 



