A Study of Sonic Grcgarincs 9 



The sarcocyte is well developed and especially thick and dis- 

 tinct over the anterior part of the protomerite. In figure 11 the 

 anterior sarcocyte is 23 /x, thick and the lateral 6 jx. This thick- 

 ening of the anterior portion of the protomerite is a common 

 feature in gregarines and perhaps has a protective function, espe- 

 ciall}' in forms with a host like Mclanopliis where the food con- 

 sists of grass, stubble, and other harsh substances through which 

 the advancing gregarine must make its way. Cross-sections usu- 

 ally show the sarcocyte to be of uniform thickness for a given 

 transverse plane, but at times one quadrant appears thicker than 

 the others. This i§ probably due to body contraction. I have 

 noticed a distinct thickening of the sarcocyte on the inner side of 

 a curved gregarine from Eritettix ; Crawley (1905) has made a 

 related observation. 



Thin cross-sections show circular fibers running through the 

 sarcocyte, especially the inner half, and the same fibers are cut in 

 cross-sections in gregarines sectioned longitudinally (figs. i. 3, 

 5). Lankester (1872) notes that in Monocystis sipuiiciili the 

 thickened anterior cortex has a set of fibers running longitudin- 

 ally. He states that this anterior cortex is eminently mobile and 

 regards the cortex as the seat of muscular activity. Leger and 

 Duboscq (1902) write similarly regarding Ptcroccphalns nobilis. 

 The fibers in Hirmocystis rigida run circularly in the tip of the 

 protomerite as elsewhere and are quite abundant (fig. 4). I have 

 occasionally noticed a twisting of the protomerite striation, show- 

 ing that the protomerite tip is capable of a slight rotation with 

 reference to the part near the septum ; this is more apt to be seen 

 in forms where the rudimentary epimerite is present. Leger and 

 Duboscq (1902) have noted in Pyxinia occasional spiral .striae 

 instead of straight striae on the epimerite, "sans doute a la suite 

 d'une torsion." 



The sea,t of muscular activity has been variously located by 

 different writers. Leidy (1851) thought he had found it in the 

 longitudinal striations ; v. Beneden (1872) located the first de- 

 scribed set of transverse fibers in Porospora gigantca just under 

 the cuticle, giving the coats in this order, a "central column, 

 . . . cortical parenchyma, and a very thin subcuticular . . . 



157 



