44 Life and Death, Heredity and Evolution 



things are directly handed on from parent to offspring. 

 These few things are of great importance, for it is these 

 that in some way provide the foundation for the new pro- 

 duction of the other structures. In the Protozoa these are 

 as follows: (1) The halves of the nuclei; in cases where 

 there exist separate active nuclei and reserve nuclei (macro- 

 and micro-nuclei), a half of each of these is passed on to 

 each of the progeny (see Figure 7). (2) Secondly, a half of 

 the general protoplasmic mass, or cytoplasm, goes to each 

 of the progeny. As we have seen, the particular organs 

 borne by this mass usually are not handed on bodily, but 

 first disappear and are then produced anew by the offspring. 

 Some few definite organs are in particular cases passed on 

 bodily, but even in these cases at least half of them must 

 be produced anew, else of course they would occur only 

 in half as great number in each of the two offspring. All the 

 precision of the process of division and handing on is seen 

 in the nucleus (see Figure 49, page 182), so that it seems 

 probable that its different parts, each so accurately divided, 

 have special and diverse functions to perform in the 

 production of the new organs of the progeny. Just what 

 part is played by each of these things that are directly 

 handed on from parent to offspring, in producing the final 

 characters of the progeny, is one of the chief questions of 

 heredity. . 



When we have gotten to our present point in the examina- 

 tion of reproduction and heredity in these creatures, we shall 

 not make the mistake of some of the earlier writers, as to 

 the inheritance of acquired characters in the Protozoa. By 

 acquired characters we mean characters that an individual 

 did not inherit from its parents, but which were produced 

 by special conditions during its life. Since the parents mere- 

 ly divide and become the offspring, it was set forth as a 



