THE VITAL PROPERTIES OF THE CELL. 



253 



by a number of experiments upon Leucophrys pattda, a species of 

 Infusorian, that only after 300 generations have been produced 

 from a fertilised individual does the generation cycle close, the 

 descendants now showing for the first time the inclination and 

 capacity for sexual conjugation. In Onychodromus grandis this 



FIG. 137. Development of Pondortna morum (after Pringsheim ; from Sachs, Fig. 411): 

 I a swarming colony ; II the same, split up into sixteen daughter-colonies; III a 

 sexual family, through the gelatinous envelope of which the individual cells are passing 

 out; IF, V conjugation of the swarm-spores; VI a newly-formed zygote; VII a full- 

 grown zygote ; VIII transformation of the contents of a zygote into a large swarm- 

 ct-11 ; IX the same, after having been set free ; X the young colony derived from the 

 Kwarm-cell. 



condition occurs after the 140th generation, and in Stylonichia 

 puslulaia, after the 130th generation. 



In multicellnlar organisms the cells, which are pi-oduced by the 



