ONTOGENESIS 



151 



PARTIAL CONJUGATION 



Cytoplasmic Conjugation (Plastogamy). In cer- 

 tain cases (slime-molds, Heliozoa, Rhizopoda) two 

 or more cells may 

 come together, and 

 the cytoplasm of 

 the cells may fuse, 

 while the nuclei 

 retain their indi- 

 viduality. For 

 this to occur, it 

 appears necessary 

 that the cytoplasm 

 should be in a pe- 

 culiarly labile and 

 plastic condition, 

 since instances 

 have been ob- 

 served and re- 

 corded of one 

 Amoeba swallowing 

 another, and later 

 egesting it with 

 its individuality 

 unimpaired, no 

 such fusion having taken place. In many of the 

 Flagellata (cf. Bodo, above) zygosis is preceded by an 

 "amoeboid" stage, which is undoubtedly correlated 

 with a more viscid and plastic condition of the proto- 

 plasm. It is impossible that there should not be 



FIG. 60. Plastogamy in a protozoan 

 (Trichosphcerium) . In three places (marked 

 with a 1) the limiting boundary of the 

 individuals is still intact. The form is multi- 

 nucleate. (From Lang, after Schaudinn.) 



