CHAPTER VIII. 



The Egg-Cell or Ovum. 



In the preceding chapter we sketched the history of the " ovum- 

 theory," which expresses the now famiHar fact that every 

 organism, reproduced in the ordinary way, develops from a 

 fertihsed egg-cell. It is now necessary to attend more carefully 

 to the essential characters and history of this "primordium 

 commune,"' this common starting-point of life, leaving the details. 



Animal Cell, showinc; the chromatin elements of nucleus 

 (a) in a long coil, and the protoplasmic network {b) round 



about. — From Carnoy. 



along with the other problems of development to a special 

 volume devoted to Embryology. 



,§ I. Structure of the Ovum. — The ovum presents all the 

 essential features of any other animal cell. There is the 



G 



