PARAMECIUM CALKINSI. 



breadth. In other words, the length is about the same as that 

 of many races of P. aurelia, but the breadth is proportionally 



FIG. i. FIG. 2. FIG. 3. 



FIGS. 1-3. Paramecium calkinsi, sp. nov. 



greater and the broadest part is anterior, whereas it is posterior 

 to the middle in P. aurelia. But, of course, no emphasis can be 

 placed on size relations since it is probable that when P. calkinsi 

 from other localities is studied, racial size differences will be 

 found to occur. 



The ciliary apparatus of the new species affords no striking 

 characteristic and an undulating membrane is present in the 

 gullet as in all paramecia. The trichocyst apparatus is partic- 

 ularly well developed. The trichocysts are relatively evenly 

 distributed in the cortical layer of protoplasm, except at the 

 anterior end where they are more closely crowded together. 

 The surface of the cell in profile presents, upon careful study, 

 a slightly crenulated outline, each of the tiny elevations repre- 

 senting the position of a trichocyst and the depressions between 

 affording the points of origin of the cilia. The structure of the 

 trichocysts as they appear in situ is shown in Fig. 4. Exploded 

 and detached examples appear in Fig. 5. 



