1911.] NATURAL SCIENCES OF PHILADELPHIA. 463 



descent gas lamp, and no trouble was experienced in getting excellent 

 definition. 



The spore, in the fixed smears, shows distinctly a differentiation into 

 a broad and a narrow end. As in the fresh material, the broad end 

 is rounded; the narrow end tapering and sometimes almost pointed. 



The cytoplasm is either homogeneous, staining solidly, or there 

 can be made out a poorly defined spongioplasm. This latter is mostly 

 confined to the broad end of the spore, where there can often be seen 

 minute vacuoles. In this part, also, rather coarse granules are fre- 

 quent, which take the chromatin stain. It was not possible, however, 

 to say whether these belong to the cytoplasm or to the nuclear appara- 

 tus of the spore. They were usually in association with the nucleus- 

 like body in the centre of the parasite, and may belong to the class of 

 the so-called metachromatic granules which have been described as 

 present in sarcosporidian spores. 



In the narrow end of the spore, the cytoplasm nearly always stained 

 homogeneously, and in many cases was so solid near the extremity 

 as to suggest a differentiation such as occurs in the anterior end of 

 Telosporidian sporozoites. In these, the cytoplasm is greatly stiffened 

 and forms a sort of beak, which enables the parasites to bore into the 

 cells of the host. This is the only indication obtainable as to which 

 is the anterior end of these spores of Sarcocystis rileyi. 



The cytoplasm takes the usual stain, being red in acid fuchsin and 

 blue in Wright's stain. 



A distinct periplast is present, which stains the same as the rest 

 of the cytoplasm. It could easily be seen in all of the smears, and 

 was well demonstrated with those fixed in Hermann's fluid, where, 

 as a consequence of the violent invasion of the cell by the fluid, it was 

 frequently torn loose from the entoplasm. 



Measurements show that there is quite a little shrinkage during 

 fixation. The fresh spores measured 14-15 microns long by 2-3 broad. 

 Those free in the smears range from 9-13.4 long by 1.7-2.3 broad. 

 In a number of cases, however, there were present in the smears 

 portions of the cysts, showing the spores still lying within the com- 

 partments. Measurements of such spores showed them to be 11.4- 

 13.0 long by 1.6-2.3 microns wide, and gave a mean of 12.2 by 2 

 microns. In these fixation is probably a trifle slower, and hence 

 there is not so much shrinkage. 



Internally, counting from the broad to the narrow end, the spores 

 show: 



(1) A vacuole. 



