in the figure, and an eighth on the back. Here (No. 9) 

 the number of cells has increased very much. As you 

 view these figures you will notice that they look very 

 much indeed like oranges divided into segments. It 

 seems, in fact, as if this egg, which was spherical in 

 form, were being divided up into a certain number of 

 segments. The process was first observed in the eggs 

 of some of the amphibia (frogs, toads and salaman- 

 ders), and it was therefore called segmentation, because 

 it was not known at that time what the process really 

 meant. We have then before us an ovum and a series 

 of stages of the segmentation of the ovum, and the 

 result of that segmentation is to produce an ever- 

 increasing number of cells which, in the last of the 

 figures upon the screen, have become so numerous 

 that we are no longer able to count them readily. 

 Every one of these cells has its own nucleus. When 

 the process of segmentation is complete and reaches 

 its final limit, we then see, if we examine that stage 

 of development, cells of the young type, such as I 

 have described to you, in which there is a nucleus 

 with a small amount of protoplasm about each nucleus. 

 It seems to me, therefore, and this is a new interpre- 

 tation which I present to you, that the process of 

 segmentation of the ovum, with which the develop- 

 ment of all the animals of the higher type invariably 

 begins, is really the process of producing young cells. 

 It is the process of rejuvenation. There is not any 

 considerable growth of the living protoplasmic ma- 

 terial of these eggs, and at the final stage the total 



