156 



ZOOLOGY 



inherited the tendencies which through untold generations have 

 resulted in safety. Those with wrong tendencies have been 

 eliminated. In this way, through generations of trial and error 

 and by adjustments on the part of the organisms they have 

 become adapted to the conditions of life. We have no evidence 



FIG. 69. 



FlG. 69. Paramecium. i, transverse fission; 2-5, stages in conjugation. Lettering as in Pig. 

 68. The meganucleus gradually disintegrates during the process and the micronucleus by two 

 successive divisions forms four micronuclei. Two of these disintegrate. One of the remaining 

 micronuclei (n) in each animal passes into the other Paramecium and unites with the stationary 

 micronucleus (n*). thus fertilizing it. Later a new meganucleus is formed in each animal by the 

 division of this body. Nucleus n* is often smaller than n and may represent the male element. 



Questions on the figure. Which is permanently represented in the cell during 

 conjugation, the micro- or the mega-nucleus? Which seems to correspond most 

 nearly to the ordinary nucleus of higher forms? What really transpires in the act 

 of conjugating? Compare this with more elaborate figures and descriptions in 

 reference texts. 



that they learn by experience. . They transmit their native 

 qualities, but not the results of accident to the individual body. 



199. Reproduction. In the Protozoa we discover methods 

 of reproduction which are to be looked upon as suggestions of 



