732 INFECTION AND IMMUNITY. 



undergo another type of proliferation. Calkins, 

 the zoologist, after studying the material, shares 

 their views and has constructed a life cycle of the 

 parasite from the various forms which he found in 

 fixed and stained preparations. 



Life History The smallest recognizable forms in the cytoplasm 

 of Cytoryctes. measure about 0.7 of a micron and lie in a vacuole in 

 the cytoplasm near the nucleus. Calkins interprets 

 these as "gemmules" and as products of the prolifera- 

 tion of the parasite at the primary point of infection 

 ( lungs (?) ) . Somewhat larger forms ( 3 microns ) con- 

 taining a vacuole with a central point staining with 

 methylene blue, represent "gemmules" which have grown 

 and have become somewhat differentiated. The periphery 

 of the organism becomes differentiated also by the for- 

 mation of minute dots which may eventually be stained 

 by a special method. During this stage the organism 



Cytoplasm! c "often is spherical, but may be fusiform, pyriform or 

 Stave*. ame ] 30 i ( j j while pseudopodia are frequently caught in 

 various degrees of extension." No definite nucleus is 

 discernible, but material corresponding to nuclear sub- 

 stance is distributed somewhat generally through the 

 parasitic cell. Certain granules are distributed through- 

 out the body of the organism, and these granules eventu- 

 ally give rise to the "gemmules" or young parasites 

 which become free by the disintegration of the mother 

 cell. 



Howard and Perkins find, in addition to the cyto- 

 plasmic stage of Councilman and his co-workers, a sec- 

 ond cytoplasmic stage, the products of which penetrate 

 the nucleus to institute the intranuclear stages. Cal- 

 kins speaks of the fate of the gemmules as follows: 

 "The germs formed by the multiplicative reproduction 

 of the cytoplasmic ameboid form of the parasite may 

 develop into new cytoplasmic organisms or ultimately 

 may become germ cells within the nucleus of the epithe- 

 lial cell. In the latter case they develop into struc- 

 tures which I regard as gametocytes. The resulting 

 zygote (formed by conjugation of the gametes) is the 

 ameboid pansporoblast mother organism." 



