CHAPTER III.

FIXED MESSMATES.

Cirrhipedes--Importance of Embryology--Recurrent Development--Messmates, characteristic of the various Species of Whales--Cirrhipedes on Sharks--Crustaceans, Messmates on other Crustaceans--Cirrhipedes on Molluscs--Bryozoa--Fossil Messmates--Messmates on Sponges--Spicules of Hyalonema--Ophiodendrum 53