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 



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, chromatin has passed into cytoplasm, leaving no definite nuclei in 

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

 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 chromatin; 

 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 (J) 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 



