SLX IN PROTOZOA 171 



Order Am o chin a 



AmoniT the accounts of sexual reproduction in amoeboid forms, 

 that for SiippiiJCii {Amoeba) diploidea (Fig. N, 1 to 6) appears to be 

 the most acceptable. First described by I lartmann and Niigler (1908) 

 and Nagler (1909), the life cycle is about as follows. This species is 

 normally binucleate, the nuclei lying close together and dividing si- 

 multaneously at each binary fission (1, 2). Under certain conditions, 

 two of these binucleate animals come together and develop a common 

 cyst membrane about them (3,4). In each amoeba the two nuclei fuse 

 in a long-delayed fertilization karyogamy. The cytosomes next fuse, 

 then each diploid nucleus undergoes a "reduction" division, one 

 daughter nucleus degenerating. A second "reduction" division pro- 

 duces a haploid nucleus and a second reduction body (5). These two 

 nuclei remain as those of the vegetative animal which emerges from 

 the cyst (6). 



The general features of this life cycle were confirmed by De- 

 schiens (193 3), who added a process of schizogony, and partially 

 confirmed by Kropp (1939). In none of the accounts are there clear 

 indications of chromosome numbers. 



In addition to his study of Sappinea diploidea, Nagler (1909) 

 also reported evidence for autogamy for Amoeba f rose hi and Amoeba 

 alba, but the accounts are not convincing. Other descriptions of sex- 

 ual reproduction in smaller amoeba are those for Avweba mimita 

 (Popoff, 1911), in which the formation of "gamete" nuclei out of 

 chromidia was reported, and for Amoeba mira (Glaser, 1912), in 

 which two maturation divisions were described without syngamy 

 having been seen. 



For Amoeba protens (Chaos diffineiis) and its close relatives 

 there are numerous accounts indicating complex life cycles, often 



Fig. N. 



1-6, Sappinea (Amoeba) diploidea, from Kuhn (1926), after Hartmann and Nagler 

 (1908), redrawn. 1, binucleate vegetative amoeba; 2, binary fission; 3, association of 

 two vegetative amoebae; 4, encystment of such a pair; 5, fusion of cytoplasms and 

 meiotic nuclear division; 6, binucleate vegetative amoeba emerged from the cyst. 7-11, 

 Euglypha sctitigera, from Penard (1938), redrawn. 7, two normal individuals attached 

 at oral areas; 8, new fusion body beginning to emerge; 9, new larger individual de- 

 rived from fusion of the two original animals; 10, encystment of "zygote"; 11, older 

 cyst. 



