2l6 



GUYER. 



[Vol. II. 



substance. Fig. 5 shows vacuolation just commencing in a 

 large single &%g. 



The sphere substance in both single and double eggs may- 

 be found in various conditions. In many places it seems to be 



Fig. 4. — X no. Four sections of a series from a large vacuolated double egg. /, follicle ; 

 n, nucleus ; /, phagocytes ; s, sphere ; v, vacuole. 



deteriorating. Besides being connected with the formation of 

 vacuoles, it seems to play some role in the formation or dissolu- 

 tion, as the case may be, of the cell wall in double eggs. It is 

 always in contact with the intervening cell membrane (Figs. 2 

 and 4, s). In the eggs of normal pigeons it remains in more or 



