170 



HEREDITY AND SEX 



into the hermaphrodites which find their way again 

 into the lungs of frogs. 



Boveri and Schleip have worked out the history 

 of the chromosomes in this case. The cells of the 



FIG. 87. Chromosomes of Angiostomum. (A), oogonia, CB), equa- 

 torial plate of first maturation division; (C), young spermatocyte 

 (D) , first spermatocyte division in metaphase ; (E) , same in anaphase 

 (F), spermatocyte of second division; (G), and (#), division of same 

 (/), and (K), loss of X at plane of division ; (L), first segmentation division 

 of a male embryo ; two sets of chromosomes (5 and 6=11 respectively) 

 separate ; (M ) equatorial plate of dividing cell of female embryo = 12 

 chromosomes ; (N) , same from male embryo =11 chromosomes. (After 

 Schleip.) 



hermaphrodite have twelve chromosomes (Fig. 87). 

 The eggs, after extruding two polar bodies, have 

 six chromosomes. The spermatozoa that develop 

 in the body of the same animal have six or five chro- 

 mosomes each, because one chromosome is lost in half 



