1 6 THE SCIENCE OF LIFE. 



globular bell becomes first flattened, then notched, and 

 lastly divided. As soon as division takes place there are 

 distinct motions in the separate individuals. In one of 

 them the cilia are absorbed, and new cilia appear on the 

 side next to the footstalk. The motions of the new cilia 

 form a current sufficient to detach the newly-formed 

 bell, which becomes isolated, swims away, and develops 

 a new stalk, after fixing itself in a new place. 



Another mode of increase sometimes occurs, in which 

 the animalcule seems to pass through a sort of chrysalis 

 state. It becomes encysted, like the primitive forms of 

 vegetables. It is first rounded, then a sort of gelatinous 

 secretion hardens into a case, protecting the interior 

 from antagonizing cold, etc. ; then the encysted body 

 breaks up into nuclei, or separate spots, and afterward 

 into numerous gemmules, or small germs, which are set 

 free by the bursting of the envelope, and swim away to 

 grow into new individuals. 



During the encysting process the Vorticella often ap- 

 pears like a globular pincushion with pins sticking in it. 

 This is now known to be caused by a parasite, the 

 Acineta, which sends forth a projecting arm into the 

 body of its host to absorb its fluid nutriment. 



7. I have selected the Vorticella for a first lesson on 

 Biology because it is quite common, and simple enough 

 for study. What can we learn here of life-force? Is 

 there such a thing as life-force ? Is there a difference 

 between the living Vorticella and the dead twig it rests 

 upon? Some philosophers, as we have seen, declare 

 that there is no difference. The old astrologers used to 

 say that all things were living, and the teachers of an- 



