XVIII. THE NATURE OF LIGHT, WITH A GENERAL ACCOUNT OF PHYSICAL OPTICS. By Dr. EUGENE LOMMEL, Professor of Physics in the University of Erlangen. With 188 Illustrations and a Plate of Spectra in Chromolithography. Price, $2.00. XIX. ANIMAL PARASITES AND MESSMATES. By Monsieur VAN BENEDEN, Professor of the University of Louvain, Correspondent of the Institute of France. With 83 Illustrations. (_In press._) THE INTERNATIONAL SCIENTIFIC SERIES. ANIMAL PARASITES AND MESSMATES. BY P. J. VAN BENEDEN, PROFESSOR AT THE UNIVERSITY OF LOUVAIN, CORRESPONDENT OF THE INSTITUTE OF FRANCE. _WITH EIGHTY-THREE ILLUSTRATIONS._ NEW YORK: D. APPLETON AND COMPANY, 549 & 551 BROADWAY. 1876. CONTENTS. vii PAGE INTRODUCTION. Adaptation of Food to Animals--Animal Manufacturers-- Brigands--Messmates--Mutualists--Theory of Spontaneous Generation xiii CHAPTER I. ANIMAL MESSMATES. Definition--Free Messmates--Fixed Messmates 1 CHAPTER II. FREE MESSMATES. Found in all Classes--Fierasfers in Holothuridæ--Pilot Fish--Remora--Crustacean Messmates--Poisoning by Mussels--Pearl Mussel and small Crab--Dromiæ--Turtle Crabs--Macrourous Decapods--Hermit Crabs--Friendship of Pagurus and Anemone--Isopods--Messmates on Whales-- Molluscan Messmates--Lerneans--Distomes--Messmates of the Echinodermata--Of Sponges--Infusorial Messmates 4 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 CHAPTER IV. viii MUTUALISTS. Definition--Ricinidæ--Trichodectes of Dog harbouring Larva of Tænia--Arguli--Caliguli--Ancei--Pranizæ--Cyami--Nematode Mutualists--Strange form of Histriobdellæ--Egyptian Distome in Man 68 CHAPTER V. PARASITES.