244 



FERTILIZATION 



DISAPPEARANCE OF 

 YOLK PLATES BEG 

 AROUND MICRO PYL 

 MICROPYLE 

 OIL DROPS 

 YOL K PLATES 

 CHORION 



V ITEL LINE 



MEMBRANE 



PER (VITELLINE S PAC 



C R PY L E 



F 



CONCENTRATION 

 P ROTO PLA S M IN 

 REGION OF MICROPYLE 



PERIVITELLINE SPACE 

 VITELLINE MEMBRANE 



Fig. 122. Changes during fertilization in the egg of Fundidus heteroclitus. (A) Egg 

 before fertilization. (B, C) Changes in the egg shortly after sperm entrance into the 

 egg. In (B) is shown the contraction of the egg from the vitelline membrane, the disap- 

 pearance of the yolk plates, and the formation of the perivitelline space. In (C) is shown 

 the migration of the peripheral cytoplasm toward the point where the sperm has entered 

 the egg, forming a cytoplasmic or polar cap. 



is a pronounced drop in the respiratory quotient, presumably indicating a 

 change in the character of oxygen consumption (Brachet, J., '50, p. 106). 

 Fertihzation does not change the rate of oxygen consumption in the teleost 

 fish, Fundulus heteroclitus, but, in the laiTiprey, oxygen consumption is in- 

 creased (Brachet, J., '50, p. 108). Also, in the egg of the sea urchin, fol- 

 lowing artificial activation or normal fertilization, there is a considerable 

 increase in oxygen consumption (fig. 120). In the unfertilized and fertilized 

 egg of the starfish (Asterias) apparently there is no change in the rate of oxygen 

 metabolism. In the eggs of certain sea urchins it has been shown by Runnstrom 

 and co-workers (Runnstrom, '49, p. 306) that acid formation occurs follow- 

 ing fertilization. It is of brief duration. (Consult also Brachet, J., '50, p. 120, 

 for references.) Other changes have been described, such as an increase in 

 viscosity of the egg (Heilbrunn, '15), and an increase in permeability of the 

 egg membrane (Heilbrunn, '15). Fertilization may produce a higher dispersity 

 of the egg colloidal material, at least in some species. Changes of a metabolic 

 nature, therefore, are a part of the fertilization picture. (The reader should 

 consult Brachet, J., '50, Chap. 4, for a thorough discussion of physiological 

 changes at fertilization.) 



