ON PARASITES IN GENERAL 1 Occasional and Permanent Parasitism 1 Entozoa, Endoparasites, Helminthes, Turbellaria 2 Hermaphroditism 4 Fertility of Parasites 5 Transmigrations 5 Commensals, Mutualists 6 Incidental and Pseudo-parasites 6 The Influence of Parasites on the Host 8 Origin of Parasites 10 Derivation of Parasites 19 Change of Host 20 Literature 22 THE ANIMAL PARASITES OF MAN 25 *A. Protozoa* 25 CLASSIFICATION OF THE PROTOZOA. Class I. SARCODINA 27 Order. _Amœbina_ 27 _Foraminifera_ 27 _Heliozoa_ 27 _Radiolaria_ 28 Class II. MASTIGOPHORA 28 III. SPOROZOA 28 Sub-class 1. TELOSPORIDIA 28 Order. _Gregarinida_ 28 _Coccidiidea_ 28 _Hæmosporidia_ 28 Sub-class 2. NEOSPORIDIA 28 Order. _Myxosporidia_ 28 _Microsporidia_ 28 _Sarcosporidia_ 28 _Haplosporidia_ 29 Class IV. INFUSORIA 29 V. SUCTORIA 29