148 



PROTOZOOLOGY 



in the trophozoite of Sphaeromyxa sahrazesi (Fig. 210), micro- 

 and macro-gametes develop, each with a haploid nucleus. Anisog- 

 amy, however, is peculiar in that the two nuclei remain inde- 

 pendent. The microgametic nucleus divides once and the two 

 nuclei remain as the vegetative nuclei of the pansporoblast, while 

 the macrogamete nucleus multiplies repeatedly and develop into 

 two spores. Anisogamy^has been suggested to occur in some mem- 

 bers of Amoebina, particularly in Endamoeba hlattae. Mercier 

 (1909) believed that in this amoeba there occurs anisogamy soon 



Fig. 73. The life-cycle of Eudorina elegans (Goebel). a, asexual repro- 

 duction; b, se.xual reproduction, a female colony with clustered and 

 isolated microgametes. 



after excystment in the host's intestine, but this awaits confirma- 

 tion. Cultural studies of various parasitic amoebae in recent years 

 show no evidence of sexual reproduction in those forms. 



Among the Ciliophora, the sexual fusion occurs only in Proto- 

 ciliata (Fig. 225) and the conjugation described below is the usual 

 method of sexual reproduction. 



Conjugation. The conjugation is a temporary union of two 

 individuals of one and the same species for the purpose of ex- 

 changing part of the nuclear material and occurs almost ex- 

 clusively in the Eucihata and Suctoria. The two individuals which 

 participate in this process may be either isogamous or anisog- 

 amous. In Paramecium caudatum (Fig. 74), two individuals 

 come in contact on their oral surfaces. The micronucleus in each 



