264 GERM-CELL CYCLE IN ANIMALS 
Reduction Ripe Eggs 
Division Polar Body 
GO 6 
is Fertilized 
oy] 
SQ) 
Fertilized 
Egg 
Oégonium 
Spermat- 
ogonium 
Sperm 
Fic. 69.— Diagrams showing the behavior of the chromosomes during 
maturation and fertilization in the starfish, Echinus. One kind of 
spermatozo6n is formed, but the ripe eggs differ, one containing a 
large X-element, the other asmall Y-element. (From Schleip, 1913.) 
x §© GQ — Wo 
Protenor, Anasa Syromastes, Homo Ascaris lumbricoides 
X 00 00 & 7) 
() ve 
Nazara Euschistus Nazara Thyanta 
viridula coenus hilaris calceata 
ee ey 
Rocconota, Prionides, Gelastocoris 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.) 
