DEVELOPMENT OF A MYXOSPORIDIAN 337 



liquid food as well. There is also evidence that the tropho- 

 zoites may ingest any small, solid particles present in the urine. 



I have been unable to find any case where the bladder epi- 

 thelium showed appreciable injury by the parasites, although 

 the presence of blood corpuscles in the urine would indicate 

 that this must occasionally occur. 



The size of the full-grown, vegetative trophozoites varies 

 somewhat, the average diameter being from 25 to 30^. As spor- 

 ulating trophozoites were found to have approximately the same 

 diameter this is believed to be the maximum size reached by this 

 form. 



Large numbers of trophozoites were observed in which the 

 spores were in various stages of development. These showed 

 practically the same characteristics as the vegetative forms, 

 except that most of the endoplasm is used up in forming the 

 spores, the fat globules which remain being crowded to one side 

 between the two spores (fig. 44). Trophozoites in which the 

 spores were matured usually disintegrated very quickly after be- 

 ing placed on the slide, thus setting the spores free. 



The spores (figs. 45 and 46) are approximately spherical with 

 an average diameter of about 15^. In a few cases the diameter 

 was found to be slightly greater in one direction than in others, 

 but this is not believed to be a constant character. The spores 

 contain two polar capsules, each having a diameter of 4.5^. 

 The length of the polar filaments after extrusion varies from 27 

 to 35//. The sporoplasm is plainly seen within the spore as a 

 rounded, finely granular mass below the polar capsules. Num- 

 bers of fat globules are often present in the spore, part of them 

 being inclosed within the sporoplasm. The sutural line, formed 

 by the junction of the halves of the spore membrane, is not 

 straight, as is the case in many species of Myxosporidia, but 

 takes a characteristic sinuous course around the spore which 

 can best be understood by consulting figure 46. Usually one 

 valve of the spore membrane is slightly smaller than the other 

 into which it appears to telescope. 



b. Preserved material. In giving an account of the results 

 obtained from the studj^ of stained material it will simplify mat- 



