ENTAMGEBA HISTOLYTICA (TETRAGENA) 



39 



its discoverer at first mistook it for a variety of that species. Accord- 

 ing to Hartmann, a distinct ectoplasm is only clearly visible when 

 a pseudopodium is protruded (fig. 5). The granular endoplasm may 

 contain ingested red blood corpuscles (fig. 6). The large, round 

 nucleus is visible in the fresh state (fig. 8, a). So-called chromidial 

 masses (? crystalloidal substances) may occur in the cytoplasm. 



Some investigators, as Hartmann, 1 lay stress on the internal 

 structure of the nucleus (fig. 8, b, c), best seen in preparations fixed wet 

 and stained with iron-hsematoxylin. The nucleus is limited by a well- 

 marked nuclear membrane, on the inside of which granules or nodules 

 of chromatin may occur. There is a karyosome, which, in success- 



e 



FIG. q.Entamceba hisiolytica (tetragena form), a, emission of chromatin from nucleus ; 

 6, nuclear division ; c, degenerating form with two nuclei ; d, e, f, cysts containing one, two 

 and four nuclei respectively, and showing chromidial blocks. X 2,000. (After Hartmann.) 



fully stained specimens, shows, at times, a central dot called a 

 centriole. (The nucleus of Entamceba coll does not contain such a 

 centriole.) However, the structure of the nucleus varies at different 

 periods during the life-cycle. 



The diameter of the trophozoites or vegetative forms (fig. 8, a] is 

 variously given as from 20 //, to 40 //,. Multiplication proceeds by 

 binary fission and also by schizogony into four merozoites. 2 



Reproduction takes place by endogenous encystment (fig. 9, d-f), 

 which is preceded by nuclear division into two, reduction and then 

 autogamy. The interpretation of the latter phenomenon as autogamy 



1 Arch.f. Protistenkitnde (1911), xxiv, p. 163. 



- See Darling, 1913, Arch. Intern. Afed., vol. ii, pi. i, fig. 3- 



