Almost all zoophytes live in the sea, but some few in fresh water; none are important agriculturally. The following belong to this sub-kingdom: 1. The =Hydroid Zoophytes= (_Hydrozoa_), including the medusæ of the North Sea, many of which are the sexual stage in the life history of fixed asexual polypes. The common =Freshwater Polypes= (_Hydra viridis_, _fusca_, etc.). 2. The =Flower Polypes= (_Anthozoa_), to which belong =Red Coral= (_Corallium rubrum_), and the =reef-building corals= (_Astræa_, _Mæandrina_, etc.). 3. The =Sponges= (_Porifera_), which are usually considered cœlenterates, though they possess no nettling organs (=Freshwater Sponge= = _Spongilla_, =Bath Sponge= = _Euspongia officinalis_). =Seventh Sub-Kingdom: PROTOZOA= (ONE-CELLED ANIMALS). [Illustration: FIG. 149.—Two species of Proteus Animalcule (_Amœba_), one with protoplasmic processes, slender and branched; the other with short blunt processes. Highly magnified. ] This sub-kingdom includes animals which are mostly microscopic, or at any rate small, and live in the sea, fresh water, or damp places. They are unicellular, and consist of a soft viscous substance (_protoplasm_ or _sarcode_) of contractile nature, and therefore capable of altering its shape. They may or may not be enclosed by a firm wall. Many secrete siliceous structures or calcareous shells. They are of no agricultural importance. Here belong: =Infusoria=, common in putrid solutions; and =Rhizopods=, such as _Amœba_, the =Proteus Animalcule= (Fig. 149), so called because its shape is constantly altering. THE END. PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES. ------------------------------------------------------------------------ OTHER WORKS BY PROF. AINSWORTH DAVIS. _Published by CHAS. GRIFFIN & CO., Exeter Street, Strand._ =A TEXT-BOOK OF BIOLOGY.= Second Edition. Part I., =Botany=, 8_s._ 6_d._ Part II., =Zoology=, 10_s._ 6_d._ “Furnishes a clear and comprehensive exposition of the subject in a systematic form.”—_Saturday Review._ “It is certainly the best ‘biology’ with which we are acquainted, and it owes its pre-eminence to the fact above stated, that it is an excellent attempt to present biology to the student as a correlated and complete science.”—_British Medical Journal._ “As a reference book ... one cannot speak too highly of this text-book, and as a treatise in theoretical biology it occupies a place not filled by any other English publication.”—_Science._ =THE FLOWERING PLANT, as Illustrating the First Principles of Botany.= Second Edition. 3_s._ 6_d._