248 



Of the four spores produced in each individual (Colpidium) all 

 but one atrophy. 



The spore individuals or sporozooids do not themselves conjugate, 

 but by virtual fission, in which the individuals produced do not be- 

 come separate, because there is no division of the protoplasm, like 

 gametes or gametozooids arise. The sexual generation thus arises 

 from the spores, or asexual generation, by fission 0- Thus the anti- 

 thetic alternation is recognisable here ; but, and all this holds true for 

 the other Infusorians to be afterwards considered, it is largely masked 

 to observation and detection, because overshadowed by the process of 

 fission, which has become so highly evolved among the Infusoria. 



Fig. 2. 



___..- /^ 



Other Infusoria present slight differences in the conjugation pro- 

 cesses, and, in order to demonstrate how mutatis mutandis the 

 "law" holds for all, short interpretations of various cases, figured by 

 Maupas and worked out by him and by R. Hertwig, may now 

 follow. 



Paramecium aurelia (Fig. 2 after Maupas). This form pos- 

 sesses two micronuclei. The conjugation is explained as follows. 

 1) A — C Two divisions of micronuclei leading to spore-formation 

 (c) and reduction. Atrophy of seven of the eight spores. 



1) Subsequent to actual conjugation the cycle contains a great but, 

 as Maupas has proved, definite number of secondarily asexual generations, 

 with duplicated chromosomes, produced by fissions. 



