THE MATURE EGG, UNFERTILIZED AND FERTILIZED 8l 



h. Effect of Age, Temperature, etc. on Size of Eggs 



Effect of: 



Age. No effect for 4 hours (Glaser, 1914a), Increase in size for first 

 23-50 hrs., measurable by 3rd hr., then decrease (Goldforb, 

 1918a, b; 1935a). 

 Temperature. No effect 5.4-29.3 °C. (Lucke and McCutcheon, 1926a; 



1935)- 

 pH. No effect 4.0-9.8° (Lucke and McCutcheon, 1926a, b), 



Amino acids. No swelHng (Lucke and McCutcheon, 1926 a). 



Ether. No effect unless injured (Lucke and McCutcheon, 1926a). 



Urethanes. No effect (Lucke, 193 1). 



Oxygen lack. Become slightly smaller (Hunter, 1936). 



i. Structure of the Egg 



Like the immature egg, the mature &gg contains oil drops, yolk gra- 

 nules, mitochondria, red pigment granules, and microsomes, all scat- 

 tered in a matrix or ground substance, and a small nucleus. The alveo- 

 lar structure of the egg protoplasm has been described by E. B. Wilson 

 (1899, ^926). Data on the various granules will be found in Part IV, 

 under the appropriate heading. Photographs of the living unfertilized 

 egg and of a stained section are shown on Plate III, Photograph i, 

 and Plate V, Photograph i. 



Nucleus. - The nucleus of the mature egg is excentric, has a diameter 

 of approximately 11. 5 ]x, is lighter than the cytoplasm, i.e., goes to 

 the centripetal pole when the egg is centrifuged. Not much structure 

 is seen in the living nucleus, and it does not take any vital dyes (E, B. H., 

 1941 c). A network of chromatin material is seen in the nucleus of eggs 

 sectioned and stained with Heidenhain's haematoxylin (see Plate V). 

 In photographs taken with ultraviolet light, the network is absorbing 

 and appears black, showing the presence of nucleic acid compounds, 

 generally considered to be of the desoxyribose type (E. B. Harvey and 

 Lavin, 1944). 



The nucleus is permeable to water and swells and shrinks in hypo- 

 and hypertonic sea water (E. B. Harvey, 1943) (Table 1 1 ; Plate XIV). 

 In 100% sea water the volume is 796 \i^ (diameter 11. 5 [x) ; in 60% 

 sea water the volume is 2,145 [l^ (diameter 16.0 jx) ; in 125% sea water 

 the volume is 382 \i^ (diameter 9.6 \x) . They recover perfectly and return 

 to normal size when replaced in sea water. The swelling and shrinking 

 of the germinal vesicle of the immature egg has been studied by 

 Churney (1941b, 1942). 



