THE PHYSIOLOGY OF FERTILIZATION 145 



HI. PHYSIOLOGICAL INDICIA OF THE FERTILIZATION 

 REACTION 



We have already considered the morphological signs 

 of fertilization but may again summarize them: (i) 

 There are invariably certain cortical morphological 

 changes, such as formation of a fertilization membrane 

 (echinoderms and nematodes), formation of a perivi- 

 telline space (most animals), and secretion of jelly 

 (Nereis, Platynereis) . (2) Maturation is set in process 

 or resumed, provided it is not complete before fertili- 

 zation. (3) In the egg a sperm aster is usually formed, 

 the sperm nucleus enlarges and metamorphoses, and the 

 germ nuclei unite. What are the immediate physio- 

 logical consequences or indicia ? 



i. Changes in rate of oxidation. Warburg (1908-14) 

 determined that the rate of consumption of oxygen by 

 fertilized eggs of the sea urchin is six to seven times 

 that of unfertilized eggs, and that the rate of oxygen 

 consumption increases progressively for some time. 

 Loeb and Wastenys (1912-13) found the increase in 

 fertilized eggs of Strongylocentrotus purpuratus to be 

 four or five to one as compared with unfertilized eggs. 

 But they did not find any significant change in oxygen 

 consumption in the starfish egg after fertilization 

 (1912). These authors also determined that membrane 

 formation by artificial means causes a comparable in- 

 crease in the rate of oxidation. The materials of 

 comminuted unfertilized eggs of sea urchins (mechanical 

 [Warburg, 1914], or by cytolysis [Loeb and Wastenys, 

 1913]) also show an equal or greater increase in oxygen 

 consumption as compared with an equal amount of 

 intact unfertilized eggs. It would therefore appear 



