138 



AMEBiE 



and it is not improbable that they will prove to be of wide geo- 

 graphic distribution, and often mistaken for Endammha or flagel- 

 lates, according to the phase of existence in which they are observed. 

 The Parasites. — As already remarked, Craigia resembles 

 some of the free-Uving soil amebse in that it passes through a 

 flagellated stage, but it differs from them in having only a single 

 flagellum instead of two. Briefly the life history of Craigia 

 hominis (Fig. 40A to F) is as follows: the adult form (Fig. 40E), 

 resembling a typical ameba, is about half the size of the dysentery 



Fig. 40. Lite cycles of Craigia. 



C. hominis (A to F). A, swarmer just escaped from cyst; B, young flagellated 

 form; C, mature flagellated form; D, same, dividing; B, amebic form before 

 encystment; F, cyst with swarmers. 



C. migrans (G to L). G, swarmer just escaped from cyst; H, young flagellated 

 form; I, mature flagellated form; /, amebic form developed by transformation 

 from 7, without any multiplication; K, mature amebic form, ready to encyst; L, 

 cyst with swarmers (note larger size and smaller number of swarmers than in C. 

 hominis). X 1000. (.\fter Barlow.) 



ameba (10 to 25 yu (^yVo to tAt of an inch) in diameter), and 

 when moving exserts several blunt pseudopodia. In addition 

 to the nucleus it possesses a structure, possibly a parabasal body, 

 which appears as a bright glistening object in the living animal 

 and stains deeply with nuclear stains. The animal multiplies 

 by simple division for a time, but eventually encysts, rotating 

 on its axis during the process of forming the double-walled cyst. 

 When fully developed the cysts (Fig. 40F) are considerably 

 larger than those of the dysentery ameba (15 At (tAt of an inch) 

 in diameter) and contain about 40 round refractive bodies, which 



