ACCOUNT OF THE GERM-CELL CYCLE 27 



a small amount of the surrounding cytoplasm, 

 from the others, thus becoming a swarm spore. 

 The swarm spores escape from the mouth of the 

 parent cell ; whereas the two primary nuclei and a 

 portion of the cytoplasm not used up in the forma- 

 tion of the swarmers die. The swarmers are not 

 all alike, being of two sizes ; the larger, which may be 

 called macrogametes, and which correspond to the 

 eggs of the Metazoa, fuse with the smaller micro- 

 gametes. The zygotes which result develop into 

 normal Arcellce. The swarmers may be supposed 

 to represent the germinal protoplasm, of which, as in 

 metazoan germ cells, the chromatin content may be 

 considered the essential portion. The conditions 

 during reproduction in other Protozoa may also be 

 explained in this way, so that germinal and somatic 

 protoplasm can be distinguished as in the Metazoa. 

 The discovery of the chromidia in Protozoa 

 led to the formulation of the hypothesis of binu- 

 clearity. Believers in this hypothesis maintain 

 that each cell contains both a somatic and propaga- 

 tory nuclear material which, as a rule, are united 

 into one amphinucleus. The somatic nuclear ma- 

 terial controls vegetative functions ; the propaga- 

 tive portion serves only for the propagation of new 

 individuals. Separation occurs rarely except in 

 certain Protozoa, where, as in Paramecium, the 

 propagative substance is represented by the micronu- 

 cleus, the somatic by the macronucleus. Since the 

 chromatin is the essential substance concerned in 

 the binuclearity hypothesis, the term dichroma- 



