56 



THE RESTING AND DIVIDING CELL 



Physiologically — it lives, moves, reproduces, and dies. If kept 

 under proper conditions, such as Woodruff and Carrell kept it in 



their experiments, protoj)lasm seems 

 to be able to live indefinitelv. 



Dr. Calkins, of Columbia Uni- 

 versity, has performed many experi- 

 ments on certain cells to show 

 the importance of the presence of 

 nuclear material. In one experi- 

 ment he used Urouychia, a one- 

 celled animal. Like its relative, 

 Paramecium, this creature has two 

 nuclei, a macronucleus and a micro- 

 nucleus. The protozoologist divided the tiny creature into two 

 fragments, each having an equal part of the macronucleus and 

 micronucleus. Both parts healed. Both grew and reproduced. 

 Then he divided a second organism unequally so that the smaller 



olied 



An amoeba was cut apart, one portion 

 bearing the nucleus. Both fragments 

 healed, both continued to move, but the 

 one without a nucleus soon slowed down, 

 came to rest, and died. The nucleated 

 portion grew and became a normal 

 amoeba. 



A Stentor, relative of Paramecium, was 

 cut in three parts. Each fragment had a 

 part of the nucleus. Each grew and re- 

 generated missing parts, resulting in three 

 new and complete animals. 



A Stylonychia was cut so that only one of 

 three fragments contained nuclear material. 

 All three swam about for a time but only the 

 portion bearing the nuclear material regen- 

 erated lost parts, grew and reproduced. 



part had little macronuclear material and no micronucleus. It 

 took in little food, grew, but did not reproduce. It soon died. 

 The larger portion of the animal, containing most of the macro- 



