DEVELOPMENT OF SPERMATOBIUM. 7 



As the intracellular protozoan grows, it gradually fills 

 out the larger part of the host's spermatogonium. The 

 nucleus of the latter, however, remains intact to the last, 

 and I am doubtful if it is really at any time consumed by 

 the parasite. Fig. \b shows this stage of the protozoan. 

 The remains of the spermatogonia! cytosome is seen out- 

 side of the edges of the protozoan. On the figure they 

 are slightly colored yellow; on the slide, however, they 

 were stained light blue by the hsematoxylon, only the nu- 

 cleolus of the spermatobium having taken the yellow stain. 

 As will be seen from this figure, the nucleus and nucleo- 

 lus of the spermatobium have obtained their full size, 

 which, however, is variable in different individuals, in 

 this instance being unusually large. The nucleus of the 

 spermatogonium shows yet plainly its chromosomes, which 

 apparently have not been in the least affected by the 

 parasite. 



FREE IMMATURE STAGE. FigS. 2, 3. 



In this stage the protozoan is seen free from the sperm- 

 atogonial host, living an intercellular life in the fluid sur- 

 rounding the various developmental stages of the sperm- 

 atozoa in the sperm-sac of the host. This mode of exist- 

 ence is kept on until after the formation of the spores or 

 sporocysts. In fig. ia is represented a young sperm- 

 atobium lately having left the spermatogonium of the 

 host. Its nucleolus is large and has taken the stain 

 deeply. The boundary of the caryosome is at this stage 

 often even forming a globe; but this is not always the 

 case, nor is it typical of this stage, as both previously 

 in the intracellular form (fig. i<5), as later (fig. 2(5), may 

 the caryotheca be wavy and irregular in outline. In fig. 

 ia the cytoplasm is seen to be differentiated, there ap- 

 pearing several pellucid vacuoles at the apex. In fig. ih 

 the cytoplasm forms a network, consisting entirely of a 



