A STUDY OF THE BASIC REPRODUCTIVE AND 

 HEREDITY PHENOMENA 



Maturation and Fertilization. — For this study tlio cuf^s of 

 Ascaris are doscrihed, but taken from another part of the uterus 

 than that supplying the cells for the study of mitosis. Sections 

 of such eggs may be mounted as the first four rows upon a slide 

 with sections arranged according to the method mentioned 

 above. 



It will be profitable to recall from lecture and textbook studies 

 what is meant by the terms somatic cells, germ cells, gametes, 

 tnicrogamete, macrogamete, ovum, spermatazoon, and zygote 

 It is also important to keep in mind that a new individual comes 

 into existence through the fertilization and development of an 

 egg, which means that: An egg (ovum or macrogamete) fuses 

 with a zoosperm (microgamete) which constitutes the beginning 

 of a new individual. That is, two independent cells fuse to form 

 a single cell (fertilized egg or zygote), which is a new individual. 



The cells in the body of each species possess a definite and con- 

 stant number of chromosomes. Since two cells fuse in the 

 creation of a new individual it ordinarily would follow that with 

 each fertilization the chromosomes would double in number in 

 each new generation. This does not occur, as is known from 

 observation. It follows, then, that as reganls the gametes some 

 provision is made whereby the normal number of chromosomes 

 is maintained. The object of the present study is that of demon- 

 strating the way in wliich this comes about. The process is 

 known as the maturation of the germ cells or their preparation 

 for the fertilizing process. 



In this species of Ascaris maturation of the egg follows the 

 entrance of the sperm. The sperm meets and enters the cytoplasm 

 of the egg which is still naked. Soon after, the walls of the uterus 

 secrete an albuminous covering about the egg and two maturation 

 divisions of the egg nucleus take place before it is ready to fuse 

 with the sperm nucleus, thus completing the formation of the 

 zygote. 



Entrance ofthe Spermatozo on into the Egg. l"]xamine enough 

 eggs of row 1 to get an idea ofthe form ofthe spermatazoon and its 



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