CHAPTER TWELVE. 

 DIFFERENT KINDS OF PARENTS. 



1. Review of Beginning of Sex in Offspring. We have 



seen that the striking differences between eggs and sperms 

 are rather constant for all higher organisms. These 

 differences are the first signs of sex; indeed they are the 

 most important elements in sex. We call the egg a 

 female gamete and the sperm a male gamete. It is 

 important to remember that the gametes are the offspring 

 in reproduction. They do not merely unite and develop 

 into offspring. When they are produced the parent has 

 "reproduced." Reproduction consists in the formation 

 and the separation of these male and female cells from 

 the parent. All the other facts of sex with which we are 

 familiar come from this starting point. 



2. Simplest Cases in Which Eggs and Sperms are 

 Found. You remember that there are no eggs and sperms 

 in the simplest form of reproduction. There we see 

 merely fission or budding from one parent, with no union 

 of any kind. The simplest unions we have discovered 

 are those of conjugation, in which two similar cells, often 

 from the same parent, unite. From this we pass gradually 

 to different kinds of gametes which regularly unite. In 

 some cases eggs and sperms are produced by the same 

 mdividual. They may be produced at the same time or 

 at different times. A parent which produces both male 

 cells and female cells cannot rightly be called either male 

 or female. It is called an hermaphrodite. The word is 



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