40 



THE FOUNDATION 



Part I 



y 



egg (cell) membrane 



3 sperm 

 chromosomes 



3 egg chromosomes 



I. Egg shortly offer fertilization 

 oecomes the first cell of the embryo. 



2. The nucleus formed by the 

 coalescence of sperm and egg 

 nuclei. Interphase. 



3. Soon after duplication of the 

 chromosome threads. Early prophase. 



4. Chromosomes shorter and thicker. 

 Aster dissolving the nuclear membrane. 

 Later prophase. 



5. Lines from centrosomes are 

 attached to each chromosome at a 

 given point. Early metaphase. 



6. Lines of force from centrosomes 

 exert a pull that separates "sister 

 chromosomes'! Later metaphase. 



7. Pulling apart of two identical 

 groups of chromosomes. Body of 

 cell dividing. Late anaphase. 



8. Two separate cells, each with a 

 nucleus of tangled threads as in 2. 

 Interphase (Telophase omitted) 



