FORAMINIFERA 



397 



{2). They grow into mature megalo spheric forms which measure 

 60-72)U in diameter. Two to four such individuals become associated 

 and transform into "fertilization cyst." (S). The nucleus in each 

 individual divides twice or occasionally three times and thus formed 

 multinucleate bodies escape from the tests within the cyst envelope 

 where many gametocytes are produced by multiple fissions. Each 

 gametocyte which contains 12 chromosomes divides into two amoe- 

 boid haploid gametes by meiosis. Gametes developed from different 

 parents presumably undergo fusion in pairs and zygotes are pro- 



FiG. 185. a, Rhabdammina abyssorum, X5 (Kiihn); b, Rhizammina 

 algaeformis, fragment of, Xl4 (Cushman); c, Saccammina sphaerica, 

 X8 (Rhumbler); d, Hyperammina subnodosa, X4 (Brady); e, Ainmo- 

 discus incertus, X20 (Ktihn); f, Silicina limitata, Xl3 (Cushman); 

 g, Reophax nodulosus, X3 (Brady). 



duced (4)- Each zygote becomes proloculum in which the nucleus 

 divides twice and when the coiled tubular chamber of test grows to 

 about three-quarters of a whorl, young microspheric individuals 

 escape from the cyst and lead independent existence (5). Myers re- 

 ports the development of PatelUna corrugata is similar to that of 

 Spirillina, except the amoeboid gametes possess 12 haploid number 

 of chromosomes. 



In Discorbis patelliformis (Fig. 184, B, 1-5), the same investigator 

 noticed no fertilization cyst during the sexual reproduction, but two 

 megalospheric individuals come in contact and flagellate gametes are 

 produced in them. The zygotes develop within the space formed by 

 the dissolution of septa between chambers and tests; the zygote 

 nucleus divides repeatedly within each zygote and forms about 40 

 nuclei before a test is secreted. In Elphidium crispa (Fig. 184, C, 

 1-5), there is no direct association of megalospheric individuals dur- 



