30 THE FOEAMINIFEEA 



Of Heterodeguia depyesm the difference is still more 

 marked, being as great as 300 to 1. 



In the megalospheric form of PoJjjdoiueUii crispa 

 Lister states that the breaking up of the nucleus 

 gives rise to numerous small nuclear bodies, each 

 of which afterwards becomes a centre of a flagellated 

 zoospore. 



The general conclusion from the observations 

 which have been made on dimorphism by some 

 authors is that, rather than a sexual difference, 

 the two forms represent alternate phases of genera- 

 tion ; for the reason that both the megalospheric 

 and microspheric tests can produce megalospheric 



yonn&. 



1 



Some recent observations by Schaudinn have 

 thrown light on the hitherto obscure and curious 

 phenomenon of fused tests often found in the 

 Foraminifera, as in Textulavia folium^ Patelliiia, 

 and Disco'biiia. This is due to the conjugation of 

 two or more individuals, whose nuclei are in a state 

 of rest, that is, not undergoing subdivision. Maupas 

 had already pointed out that by long-continued 

 fission the lower forms of life were liable to weaken- 

 ing and final extinction, but by fusion of the proto- 

 plasm and contents the organism undergoes re- 

 juvenescence. The process of fission of the nucleus 

 has been termed Karyogamy, and the process of 

 fusion of the cytoplasts Plastogamy. Hartog defines 

 Plastogamy as the cytoplastic union of cells without 



1 ' Ueber Hastoganiie bei Foraiu.,' Sit^:. Gesellsch. iiatnrforscli. 

 Freitnde, 1895, No. 10. 



