REPRODUCTION AND EARLY DEVELOPMENT. Ill 



these two layers, of the beginnings of all the special organs 

 of the adult. This comes about through continued cell 

 division, growth, and cell differentiation. 



7. If the embryonic growth is steady and the organism 

 hatches out with the organs and form of the adult the 

 development is called direct. If the embryonic stage 

 differs strikingly from the adult it is said to undergo a 

 metamorphosis. 



8. Animals begin life much alike and become gradually 

 more different as they approach their mature condition. 

 The more nearly alike they are in the adult the longer 

 is their development parallel. 



9. Every individual gets some of its qualities directly 

 from the fertilized ovum ; others it gets from the external 

 conditions. The former are hereditary. The two great 

 questions we are trying to answer about heredity are: 

 What qualities are capable of being inherited? and, How 

 are these qualities lodged in the ova and sperm? 



119. Supplementary topics for themes in Zoology and 

 English. 



1. What are the distinctions between an egg and an 

 ovum? Illustrate. 



2. The maturation of the ovum. The steps in it and 

 its supposed value and purpose. 



3. What are the evidences that the cells of the body 

 grow "old"? 



4. Parthenogenesis in the animal kindgdom. Its oc- 

 currence and possible value. 



5. The real differences between budding and equal 

 division. 



Differences between the metamorphosis of the frog 

 and that of the house-fly. 



