142 CONJUGATION, MATURATION, AND FERTILIZATION 



cated because of the formation of definite nuclei from idiochromidia, 

 and because of so-called maturation divisions of these nuclei before 

 union (coli and muris'). 



Here, again, the early observations of Schaudinn ('03) upon Enta- 

 meba coli have been fully confirmed by Craig ('08) and their conclu- 

 sions have been fully supported by Wenyon ('07) in connection with 

 E. muris, a closely allied intestinal parasite of the mouse, and by 

 Hartmann ('07) upon Entameba tetragena in man. Schaudinn's 

 excellent description was not accompanied by illustrations, but the 



FIG. 59 





! 





Autogamy in Entameba (ameba) muris. (After Wenyon.) A, ordinary ameboid form 

 with nucleus in process of division; B, ordinary individual encysted and with one nucleus; 

 C, nucleus divided; D, ehromatin has passed into cytoplasm, leaving no definite nuclei in 

 the cyst; E, two small nuclei reformed from the scattered ehromatin, other ehromatin 

 residue and food remains are being voided; F, two nuclei and so-called "reduction" bodies 

 remaining in cyst; G, a cyst with two spindles, food remains, and some waste ehromatin; 

 the two spindles give rise to four nuclei which conjugate two and two; H, cyst with two 

 recently conjugated nuclei which next divide to form four (/) and finally eight (7) spore 

 nuclei. 



corresponding stages may be illustrated by Wenyon's figures of E. 

 muris. Here and in E. coli the organisms encyst after a period in the 

 intestine; the nucleus of the encysted cell divides (Fig. 59, A, B, C) 

 and the cell body indicates a corresponding division into two parts, 

 but the connections between these parts is never lost, and we are thus 

 dealing at the beginning of fertilization with a binucleated cell. The 

 nuclei next fragment, forming idiochromidia, from which two much 

 smaller nuclei (D, E) are formed by segregation of the scattered 

 granules. Each nucleus then divides twice, one-half of each division 

 forming nuclei which degenerate in the cell (reduction nuclei) and two 



