THE SPOROZOA 



319 



pear-shaped body, 3-3 to 4 //, in length, strongly refringent and perfectly 

 hyaline in appearance, limited externally by a thin pellicle, and con- 

 taining a single nucleus at the broader end. The remarkable fact was 



m 



/ ? 



^Jofe.---" 



& 





n- 



/ 



^||^4 S&&f$98&e 

 **&* j 





FIG. 127. 



Phases of Schewiakoff's internal parasites of Cydopidat. a and 6, free amoebae; c, com- 

 mencement of encystation ; d, cyst with one nucleus ; e, cyst with many nuclei ; /, cyst one day 

 old, with six spores (sp) and a number of free nuclei () ; g, cyst three days old, full of spores 

 in a residual matrix ; h, plasmodium with three nuclei ; i, the same later, with one nucleus ; 

 j, plasmodium preparing for sporulation, with numerous nuclei and vacuoles (vac) ; k, encysted 

 plasmodium, containing numerous spherical sporoblasts ; I, later stage of the preceding, the 

 sporoblasts having become ripe spores ; m-q, stages in the division of a spore ; r, small 

 amoebulae liberated from spores. (After Schewiakoff [135], a-l x 1500 ; m-r x 2600.) 



observed that the spores multiply by fission in the cyst, their nuclei 

 dividing by a process of karyokinesis which Schewiakoff has studied and 

 figured in all its details, and which is followed by an oblique division of 

 the whole spore (Fig. 127, m-q). Besides spores dividing in this way, 



