264 



GERM-CELL CYCLE IN ANIMALS 



Reduction 

 Division 



Ripe Eggs 



Q»i P'^^f^r Body 



Oogonium 



^\y 



1// < 



Spermat- 

 ogonium 



'-/V 



s^/^ 



/w 



Fertilized 



Egg 



Fertilized 



Egg 



Fig. 69. — Diagrams showing the behavior of the chromosomes during 

 maturation and fertilization in the starfish, Echinus. One kind of 

 spermatozoon is formed, but the ripe eggs differ, one containing a 

 large X-element, the other a small Y-element. (From Schleip, 1913.) 



X 



T 



om 



Protenor, A^iasa Syromastes, Homo Ascaris lumhricoides 





Nazara 

 viridula 







V 



Euschisfus 

 coemis 



6 



Nazara 

 hilaris 



i i 







Thy ant a 

 calceata 



Rocconoia, Prionides, Gelasfocoris Acholla 

 Fitchia Sinea multispinosa 



Fig. 70. — Diagram showing the number and size relations of the X- and 

 Y-chromosomes in a number of animals. {From Wilson, 1911.) 



