DEVELOPMENT OF A MYXOSPORIDIAN 345 



to those described as hematoidin in Myxidium lieberkiihni, but 

 they always lie free in the endoplasm and are never enclosed in 

 fat globules as in that species. In many cases erythrocytes were 

 observed in the endoplasm (fig. 57). In fact they are more fre- 

 quently found in the polysporous than in the disporous tropho- 

 zoites. As in the disporous forms a careful study of both living 

 trophozoites and sections has convinced me that erythrocytes 

 are actually enclosed within the endoplasm and are not always 

 simply adhering to the exterior of the body as often happens. 

 This is clearly shown in the case of sections where there can be 

 no doubt as to their position. Many of the refractive and other 

 granules in the endoplasm are indistinguishable from those 

 found floating freely in the urine and attached to the exterior 

 of the body, and have probably been ingested in the same way 

 as the erythrocytes. 



Very often the endoplasm contains several rounded bodies 

 (fig. 59) composed of an outer hyaline layer surrounding a granu- 

 lar central portion which contains numerous refractive granules. 

 As will be described later, these bodies are gemmules which 

 make their way out of the parent and develop into daughter 

 tropozoites. 



Occasionally a large trophozoite was found containing a num- 

 ber of spores which were in all respects identical with those 

 formed by the small disporous individuals. In the large tropho- 

 zoites, however, there are always more than two spores and 

 sometimes they are so abundant as almost to fill the entire body. 

 Large trophozoites containing spores were never abundant and 

 many fish were examined in which no sporulating individuals 

 of this type were found. 



Soon after being removed to the slide the trophozoites begin 

 to send out numerous long, slender, branched pseudopodia 

 from the large anterior end of the body. These pseudopodia 

 when first formed are composed entirely of ectoplasm but later 

 endoplasm may flow into the proximal portion. Still later, 

 especially in smaller individuals, nearly the entire body may 

 take part in the formation of pseudopodia so that the trophozoites 

 may assume very irregular and grotesque forms (text figs. C and 



