THE FERTILIZATION OF AMCEBA PROTEUS. 22 5 



as I have now shown it to occur, in a manner quite unlike that of 

 the majority of other rhizopods that we know, the reason for its 

 being overlooked becomes apparent. Many have observed 

 Amceba proteus in the multinucleate condition. Carter in 1863 

 observed as many as 70 nuclei in specimens ol Amceba prince ps 

 which is usually regarded as the same as our Amoeba proteus, and 

 Wallich in the same year observed the liberation of many fine 

 granular bodies by the rupture of the nuclear membrane, while 

 Schaudinn l calls attention to the fact that he has observed the 

 nuclear multiplication and suggests that it betokens a possible 

 sexual phase. 2 



The process of fertilization, as I have described it here, comes 

 under the head of the conjugation phenomena known as endog- 

 amy, or conjugation of nuclei within the original cell parent. 

 It is not the only instance of such a phenomenon amongst the 

 Sarcodina. Hertwig, in 1898, described self-fertilization in the 

 case of Actinosphcerium, while Schaudinn in 1903 {loc. cit.) de- 

 scribed it in the case of Entamoeba coli, the harmless commensal 

 of the intestine. In both cases, however, the process is described 

 as much more complicated than that which I have outlined here. 

 In Actinosphcerium the vegetative nuclei are reduced by fusion or 

 by absorption to a relatively small number. The cell then divides 

 into as many daughter cells as there are nuclei (five to ten) ; these 

 daughter cells encyst within the parent cyst, the nucleus divides 

 by mitosis and each of the cysts divides into two daughter cysts, 

 each with one nucleus. The nucleus in each of these daughter 

 cysts next divides twice, giving rise to two " polar body " equiva- 

 lents. The cytoplasm and remaining nuclei of the two daughter 

 cysts then fuse and the fertilization is completed by the reunion 

 of the parts. In Entamoeba the process is more like that of 

 Amceba as described here. The cell throws out foreign matter 

 and waste products of its own metabolism, and becomes smaller, 

 more compact and more spherical. After secreting a gelatinous 

 membrane in which the cell remains encysted, the cell nucleus 

 divides into two nuclei, the division being followed by an incom- 



1 " Untersuchungen iiber die Fortpflanzung einiger Rhizopoden," Arb. a. d. Kais. 

 Gesundh., XIX., 1903. 



2 For further historical data see my original paper. 



