1914.] NATURAL SCIENCES OF PHILADELPHIA. 215 



tion, however (500 to 1000), it was easy to see that the wall was 

 composed of a great number of papilliform processes, standing closely 

 packed together upon a sort of basement membrane and with their 

 outer ends wholly free. That is, the cyst wall, at least in this case, 

 does not consist of a membrane pierced by pores, nor of a congeries 

 of rods bounded both without and within by a membrane, but of 

 rods or papillae projecting freely from a basement membrane. 

 Furthermore, in this case, there was nothing to show that any part 

 of the cyst wall was derived from the surrounding host tissue. 



As already stated, the papillae rested upon a basement membrane 

 with which they were apparently continuous. Within there was 

 to be seen the structure usual for sarcosporidian cysts; that is, a 

 division of the central space into compartments, the walls of which 

 were a continuation of the membrane inclosing the cyst. Finally, 

 in the central portions of the cysts there was a small area free of 

 spores, and here the coarsely alveolar structure of the frame work 

 could readily be seen. This is in itself an indication that these cysts 

 were young rather than old, since it is a matter of common obser- 

 vation that in old cysts there is always present a central space of 

 considerable extent in which there are no spores. 



As is usual, the cysts were closely packed with spores which 

 showed a certain disposition to be arranged in files, radiating from 

 the centre to the periphery. 



A study of the spores themselves revealed data of considerably 

 greater interest. Several mounts were prepared by smearing out the 

 contents of the cysts on slides, drying, fixing in absolute alcohol and 

 staining in Giemsa. As thus prepared, the spores measured about 

 13/'- long by 5.'j- wide, the precise figures for the average of 20 specimens 

 measured being 13. 14/^- long by 5.16/^- broad. The longest spore 

 measured was 16/'- long, the broadest 6/'- wide. The figure given for 

 the length, however, is a trifle too small, since the measurement was 

 taken in a straight line, no allowance being made for the curvature. 

 Furthermore, it is not unlikely that the fixed spores are too wide, 

 since they are quite large enough to be flattened in the process of 

 fixation. 



The spores, although possessing the typical banana shape, are not 

 quite symmetrical, it being generally possible to distinguish between 

 a narrower, more pointed and a broader, more rounded end. This 

 narrower end, which may be regarded as anterior, is occupied by a 

 very solid mass of homogeneous cytoplasm, which has but little 

 affinity for the stain and contrasts very sharply with the deeply 



