26 THE ORIGIN OF MAN 



There are many more species of corals but 

 these illustrations I think will be sufficient. Be- 

 fore we proceed with the second division let us 

 make a brief resume of corals. In the first place 

 they are all exclusively marine, that is living on 

 the shores, in shallow waters and in many in- 

 stances in deep waters. They feed on animals 

 but in cases where they are very minute they feed 

 on microscopic animals or plants. They multi- 

 ply either by sexual reproduction or by budding. 

 Sexual reproduction as a rule involves two 

 parents and the production of two kinds of germ 

 cells, the eggs and sperms. It is usually brought 

 about by the union of a sperm cell with an egg, 

 or less commonly by the development of the egg 

 without union with a sperm. Another method 

 of reproduction is by budding. The bud starts 

 as a protrusion of protoplasm in a small area of 

 the surface of a protozoan cell or as a localized 

 proliferation of cells. The protuberance grows 

 until it assumes the form and perhaps the size of 



