6 Vertebrate Embryology 



lighter portion which makes up the greater 

 part of the egg and which is known as the 

 cytoplasm, and a darker, spherical portion which 

 lies in the cytoplasm and is known as the 

 nucleus (germinal vesicle). Inside of the nu- 

 cleus may be seen one or more small areas, 

 the nucleoli (germinal spots) 



FIG. 2. EGG OF STARFISH. (After Gegcnbaur.) 



a. Granular protoplasm. 



b. Nucleus (germinal vesicle). 



c. Nucleolus (germinal spot). 



By the use of more refined methods and 

 higher magnification many other details of 

 structure might be brought out, but for these 

 the reader is referred to more extensive text- 

 books. 



The frog's egg is several thousand times the 

 bulk of the egg of the starfish, being about 

 1.7 mm. in diameter. This increase in size is 



