102 



THE EGGS OF MAMMALS 



TABLE XVII (Continued) 



The Development of Unfertilized Rabbit Ova in Culture. (From 



Pincus, 1930) 



(C = Chicken. 



R = Rabbit. 



Plasma. 



E = Embryo Extract.) 



The primary and surprising fact evident from the data 

 is that a majority of the ova placed in culture underwent a 

 certain degree of development, so that out of 213 eggs cul- 

 tured, 136 or 63.8 per cent are classified as having ^^ divided," 

 the term ^'divided" including any degree of observable 

 development beyond the 1 -celled state of the ova as re- 

 covered from the animals. It was the primary objective 

 of these investigations to ascertain the nature of the various 

 degrees of development undergone in vitro and to establish 

 any relationship that might exist between the age of the 

 ova and the nature of the development. Before undertaking 

 any detailed analysis of the data it is deemed advisable to 

 describe the various types of development observed. 



The ova observed in the 2-cell stage varied in appear- 

 ance as shown in Plate VIII, Figs. 1-3. The great major- 

 ity of them resembled that of Figure 1, and showed usually 

 one, sometimes two or three, polar bodies. The ovum of 

 Figure 3 was photographed after the egg had been in cul- 



