LIEK i'UOCESSES OE ANIMALS 3G5 



and echinodernis, and in some mollusks antl worms these 

 cells emanate from two different indivitluals, male and 

 female. Both kinds of cells may be produced by the same 

 individual. For example, each earthworm produces lioth 

 the sperm cell and egg; ceU. Hydrte, sea anemones, jelly- 

 fish, and many worms are bisexual; that is, produce both the 

 sperm cell and egg cell. After the sperm cell unites with, 

 or fertilizes the egg cell, development of the embrvo begins. 

 The process of growth has been described in Chapter III. 



