314 



THE SPOROZOA 



which the protoplasmic contents divide up in a few days to form a 

 number of cylindrical germs, resembling sporozoites (Fig. 125, k, I). In 

 the winter cysts are formed with a tough envelope, the contents of which 

 remain dormant until the spring and then emerge. The contents of each 







Fio. 125. 



Amoebidivm parasiticwm, Cienk. . phases of the developmental cycle, o, full-grown tube with 

 numerous nuclei (n) ; b, young tube with a single nucleus ; c, a tube divided up by oblique 

 partitions into daughter-tubes ; d, a tube divided up by transverse and longitudinal cleavages 

 into amoebulae, one of which (am) is seen emerging from the tube ; e, a tube containing freely 

 moving amoebulae ; /, g, h, free amoebulae ; i, an amoebula com to rest and of spherical 

 form, with a large vacuole ; j. the form has become oval and the spore-membrane is beginning 

 to appear at the surface ; k, I, summer-spores, with sporozoites ; m, a winter-spore, with thick 

 cyst-wall ; n, the contents of the winter-spore escaping ; o, the contents of a winter-spore, 

 which, after escaping from the cyst, have developed into a thin-walled spore containing sporo- 

 zoites, similar to a summer-spore ; p, q, young Amoebidia produced from sporozoites. (After 

 Cienkowsky ; /, g, and h are magnified 380 diameters, the other figures 285.) 



such cyst, after liberation, may either become a young Amoebidium at 

 once or may divide into two small Amoebidia, or may undergo the same 

 development as the thin-walled summer-cysta (Fig. 125, m-q). Each of 

 the eporozoitea, as they may be termed, formed within the cyst becomes 

 a young Amoebidium when liberated. 



