FERTILIZATION 597 



sexual (macrospheric generation = gamont) and asexual (microspheric 

 generation = agamont) generations occurs, and the two generations 

 may be distinguished morphologically, chiefly on the basis of the rela- 

 tive size of the original chamber of the shell. The protoplasm of the 

 two adult generations was said to fragment, to produce flagellated iso- 

 gametes from the gamont and agamete amoebulae from the agamont. 

 Fertilization occurs free in the water, and the zygotes develop into 

 agamonts, while the amoebulae develop directly into new gamonts. The 

 nuclei of both the agametes and the gametes were said to arise from 

 chromidia which are derived from the fragmentation of the primary 

 nuclei. 



In recent studies on the Foraminifera, Myers (1935, 1936, 1938) has 

 confirmed the earlier work of Lister and Schaudinn, except for the origin 

 of the gamete and agamete nuclei. In Patellina corrugata, ?olystomellina 

 crispa, SpirilUna vivipara and Discorbis patelUfoym/s, the nuclei of all 

 stages, according to Myers, are derived by an orderly process of mitotic 

 divisions from preexisting nuclei. He believes that the chromidia are 

 "concerned with feeding and metabolic activities" and in no case give 

 rise to nuclei. This is another blow to those who hold to the chromidial 

 origin of nuclei in Protozoa. 



Myers (1935) further states that gametic reduction occurs in Pa- 

 telUna corrugata and that the haploid number of chromosomes is twelve. 

 These observations differ from those of Schaudinn on the same species. 

 In P. corrugata and in S. vivipara, the isogametes are amoeboid, but in 

 D. patelliformis and Polystowellina crispa they are biflagellated, as indi- 

 cated by the earlier workers. 



In some forms, two or more gamonts become more or less closely as- 

 sociated in a kind of pseudoconjugation known as a syzygy, wherein the 

 pseudopodia may temporarily fuse with those of close neighbors, while 

 in other species they may encyst in a common capsule. This intimate 

 association possibly has a synchronizing effect on gamete formation. 



Le Calvez (1938) supports Myers's contention that gamete nuclei 

 are not derived from chromidia, but arise by mitotic divisions from pre- 

 existing nuclei. In Iridia lucida, he states, the secondary nuclei "disinte- 

 grate" by rapid divisions which at first are typically mitotic. Later, be- 

 cause they are so small and the character so obscure, the mitoses are 

 recognizable more by the centrosome than by the clarity of the chromo- 



