MATURATION PHENOMENA 



213 



The Maturation Divisions --The maturation divisions in male 

 and female organisms, while similar so far as the chromatin is 

 concerned, do not result in the formation of the same number 



MALE 



SPERMATO - 

 60NIA 



PRIMORDIAL GERM-CELLS 

 WITH DIPLOID NUMBER OF CHROMOSOMES X 



(x-4 IN THIS DIAGRAM) 



FEMALE 



MULTIPLICATION PERIOD 



MANY GENERATIONS/'? 

 SPEffMATO OOGONI, 



GROWTH PERIOD 

 5YNAP5IS 



UNION OF CHROMOSOMES IN PAIRS 

 of?MiN& f (HAPLOID NUMBER) OF BIVALENTS 



PRIMARY 

 SPERMATOCYTE 



SECONDARY 

 SPERMATOCYTE 5 



SPERMATIDS BECOME SPERMATOZOA 



0IVALENT5 LONGITUDINALLY SPLIT 



FIRST MATURATION DIVISION 



SPLIT CHROMOSOMES 



OOGOIN'A 



SECOND MATURATION DIVISION 



SINGLE 



PRIMARY 06CYTE 

 (OVARIAN EGG) 



SECONDARY OOCYTES 



EGG - I" POLAR BODY 



] POLAR BODY 



(w SOME CASES) DIVIDES 

 'MATURE OVUM " Z" POLAR BODY 



FERTILIZATION 



FIR3T CLEAVAGE 



FIG. 90. Diagram of the maturation divisions of the male and female germ 

 cells. Four chromosomes are present in all cells of the body of the case illus- 

 trated. (The polar bodies are represented as much larger than they actually are 

 in relation to the egg cell.) 



of mature germ cells. From each primordial egg cell only one 

 mature egg is formed, while three rudimentary eggs called polar 

 bodies are formed, which have no part in development, but de- 

 generate and die. From each primordial cell of the spermato- 



