1916.] NATURAL SCIENCES OF PHILADELPHIA. L5 



this sort, which have appeared in the literature from time to time, 

 seem to be due to an unfortunate desire to correlate the Sarcospo- 

 ridia with the Myxosporidia. These two groups may of course be 



closely related, bu1 as yet there is no conclusive evidence on hand 

 to show that they are. 



Plate I. figs. 3 and 1 show spores in the cells of int. 9 of mouse 2.51, 

 a l|-hour stage. It is to be noted that each of these lies in a vacuole. 

 Probably they have not been in the cells for more than an hour. 

 In both of them the cytoplasm is dense, compact, and deeply staining. 

 In both of them, also, the nucleus has enlarged and is separated from 

 the periplast only by very narrow strips of cytoplasm. 



There is, however, a difference in the nature of the net in these 

 two nuclei. In the case of fig. 3, the meshes in the centre are solidly 

 filled with chromatin, whereas in that of fig. 4 the chromatin is divided 

 into separate masses. In all of these early stages the chromatin has 

 a low affinity for stains, and, following the rule which seems to hold 

 generally true in Protozoa, takes the acid rather than the basic 

 -i a ins. On this account it results that these nuclei are rather difficult 

 microscopical objects, and seen with powers of less than 1,000 diame- 

 ters, a nucleus like that of fig. 3 looks like a vesicle containing only a 

 central granule. But with a magnification of 1,500 to 2,000, and an 

 intense artificial light, the structure as shown in the figure is brought 

 out. As will be shown later, fig. 3 represents the more primitive 

 condition, in which the chromatin is concentrated into a single mass, 

 within which, however, the meshes of the nuclear net can be traced. 

 In the case of fig. 4, the chromatin occurs in separate masses and the 

 central meshes of the net are largely clear. Nuclei precisely like 

 either of these may be seen in spores in the lumen. 



Mouse 24S. — Mouse 248 was killed two hours after feeding. Its 

 intestine was cut into 32 pieces, int. 32 representing the extreme 

 posterior portion. Observations were made on int. 3, 9, 15, 21, 27, 

 and 32. In the upper portions there were scattered spores in the 

 lumen and occasional specimens in the cells, but, following the 

 general rule, parasitization was not extensive until the more posterior 

 parts were reached. 



Plate I, fig. 5, from int. 27, shows a parasite lying in the usual vacuole 

 close to the free edge of the epithelium. The cytoplasm is dense, 

 while the nucleus shows very distinctly a nuclear net supporting 

 scattered chromatin granules. The nucleus, in this case, lies near 

 one end of the cell. Fig. 6, from int. 30, also represents what is 

 clearly a very early stage. The cytoplasm is dense and compact. 



