444 



PROTOZOOLOGY 



based upon the morphological characteristics of the nucleus. Sum- 

 mary No. 99 of 'Opinions Rendered' by the International Commis- 

 sion of Zoological Nomenclature (1928) holds that Entamoeba is a 

 synonym of Endamoeba; in the present work, however, Endamoeba 

 and Entamoeba are separated, since the two groups of species placed 

 under them possess different nuclear characteristics (Fig. 187). No- 

 menclature (Dobell, 1919, 1938; Kirby, 1945; Hemming, 1951). 



Genus Endamoeba Leidy (1879). Nucleus spheroidal to ovoid; 

 membrane thick; in life, filled with numerous granules of uniform di- 

 mensions along its peripheral region; upon fixation, a fine chro- 

 matic network becomes noticeable in their stead; central portion 



® 



Fig. 187. Diagram showing the stained nuclei of the trophozoites of 

 five genera of parasitic amoebae, a, Endamoeba; b, Entamoeba; c, Ioda- 

 moeba; d, Endolimax; e, Dientamoeba. 



coarsely reticulated ; with several endosomes between the two zones 

 (Fig. 187, a) ; in some, cytoplasm becomes prominently striated dur- 

 ing locomotion; in the intestine of invertebrates. 



E. blattae (Biitschli) (Fig. 188). In the colon of cockroaches; 10- 

 150 n in diameter; rounded individuals with broad pseudopodia, show 

 a distinct differentiation of cytoplasm; elongated forms with a few 

 pseudopodia, show ectoplasm only at the extremities of the pseudo- 

 pods; endoplasm of actively motile trophozoites shows a distinct 

 striation, a condition not seen in other amoebae; fluid-filled vacuoles 

 occur in large numbers; amoebae feed on starch grains, yeast cells, 

 and bacteria, all of which coexist in the host organ; cysts, 20-50m 

 in diameter, commonly seen in the colon contents, with often more 

 than 60 nuclei. The life-cycle of this amoeba is still unknown. Mer- 

 rier (1909) held that when the multinucleate cysts gain entrance to 

 the host intestine through its mouth, each of the cyst-nuclei becomes 

 the center of a gamete; when the cyst-membrane ruptures, the 

 gametes are set free and anisogamy takes place, resulting in forma- 



