MATURATION OF GERM CELLS 



485 



ol' the sui-rat'C'-iiK'mhi'uiie ol" tacli of tlir (laughter cells. These 

 (laughter cells adhere to oue another but do not coalesce. From 

 this it is inferred that the cell ineinhrane is insoluble in the sur- 

 rounding medium and in the cytoplasm as well. (It has been 



Priinoniial {jcriii crll. 



S])priimtogonia. 



■ IJivision period (the number of 

 divisions is iiuich greater). 



^ratllration iierioil. 



Growth jjeriod. 

 Primary spermatocyte. 



Secondary spermatocytes. 



Spermatids. 



Spermatozoa. 

 Fig. 99. — Scheme of the Processes involved in the Maturation of Spermatozoa. 



Primordial germ cell. 



Oogonia. 



Primary oiicyte or ovarian egg. 



Secondary oocytes (egg and 



first polar body) 



Mature egt; and three polar bodies. 



Division period (the number of 

 divisions is much greater). 



Growth period. 



Maturation period. 



Fic. 100. — Maturation of Ovum. 



proved experimentally that hanging drops coalesce if their surface 

 films are soluble in the drops themselves, while they separate if 

 the film is soluble in the surrounding medium.) 



Maturation of Germ Cells. The cells of the body may be divided 

 into somatic or true l)ody-cells and gonads or reproductixe cells. 

 Certain of the cells of the gonads become germ cells. The process 



