PREFACE. vii 



this subject, the author has to record here his thanks to Messrs 

 A. & C. Black for their kindness in permitting him to use 

 several of the engravings (viz., figs. 61, 64, 65, 66, 69, 71, 

 73> 75> 7^, 209, 211, and 212) from his articles on Corals 

 and Cuttle-fishes in the ninth edition of the ' Encyclopaedia 

 Britannica.' 



The only other point which appears to require notice relates 

 to the classification here adopted. This classification, as in 

 the previous editions of the work, is based essentially upon the 

 views put forth by Professor Huxley in his masterly treatise, 

 entitled ' Lectures on the Elements of Comparative Anatomy,' 

 published in 1864. The reader will find a good many minor 

 changes in this classification, necessitated by the recent pro- 

 gress of Zoological science. Thus, the new groups of the 

 Hydrocorallinae and Helioporidse of Mosely have been duly 

 recognised ; the discovery of the tracheal system of Peripatus 

 has enriched the Myriapoda with a new order: the Therio- 

 dontia of Owen have been added to the already numerous 

 groups of the extinct Reptiles ; the orders Odontolcae and 

 Odontotormae of Marsh, collectively forming the new sub-class 

 Odontornithes, are accessions to the class of Birds ; and through 

 the researches of the last-named distinguished palaeontologist, 

 the domain of Mammalian life has been extended by the estab- 

 lishment of the Tillodontia and Dinocerata. 



In the main, however, the author has not thought it neces- 

 sary to depart from the broad outlines of the systematic 

 arrangement of animals originally adopted by Professor Hux- 

 ley, to which he finds himself still able to give his hearty 

 adhesion. The student of some of the more recent German, 

 American, and English zoological publications would, how- 

 ever, find himself confronted with a classification of more 

 modern origin, and in many fundamental points essentially 

 different from the one followed here. Thus, to speak only of 

 conspicuous instances, he would find the Sponges placed with 

 the Coelenterata ; the Rugose Corals would be side by side 

 with the Jelly-fishes in the class of the Hydrozoa ; the Polyzoa 

 and Brachiopoda would be met with in the " Vermes," in the 

 immediate neighbourhood of the Annelides ; and in looking 

 for the Tunicates he would either have to direct his search to 



