56 Bihliographical Notices. 



cially those raised by the promulgation of the Darwinistic theory of 

 evolution. 



In connexion with the system of classification adopted we may 

 remark that Dr. Nicholson has separated the Sponges from the Pro- 

 tozoa, but without uniting them with any recognized group of the 

 Metazoa — he treats them " as a separate subkingdom under the 

 name of Porifera." In this course, considering the difficulties sur- 

 rounding all attempts to deal with the Sponges, we think he is in 

 the right, judging from our present lights, and he carefully indicates 

 Bome of the difficulties in question arising from the peculiaiities of 

 certain constituent elements of the sponge-body. 



The Coelenterata are treated in considerable detail and evidently 

 with reference to recent investigations, especially those of Prof. 

 Moseley on the Hydrocorallinse. It may bo noted in passing that 

 Dr. Nicholson cannot be charged with taking part in that " conspi- 

 racy of silence " upon which the Duke of Argyll descanted so elo- 

 quently in a recent number of ' Nature.' He even says that the 

 recent researches of " Semper, Murray, Guppy, &c. have shown that 

 Darwin's theory cannot be accepted as a universal explanation of 

 the mode of origin of atolls and barrier-reefs, even if it be partially 

 true." 



Prof. Huxlej's subkingdom Annuloida is given up by Prof. 

 Nicholson, "who, however, retains the class Scolecida, as including 

 the whole of the Entozoa, the Turbellaria, the free Nematoid worms, 

 and the Eotifera — a somewhat incongruous assemblage, the principal 

 distinctive characters of which are the presence of a water-vascular 

 system and the absence of a ventral chain of ganglia. The remainder 

 of the Annulosa are divided into Auarthropoda and Arthropoda, and 

 the classification adopted is that generally employed by systematic 

 zoologists. The weakest portion of this section, and, indeed, of the 

 whole book, seems to us to be that treatii^g of the Insecta ; but this 

 is a reproach which may be made to most text-books of zoology. 

 The division Molluscoidea is still retained for the Brachiopoda and 

 Polyzoa, the Tunicata being inserted between the MoUusca and 

 Vertebrata. The latter are treated at very considerable length, 

 occupying three eighths of the systematic portion of the book ; but 

 the space bestowed upon them is certainly well employed, and this 

 section furnishes one of the best guides to the structure and classi- 

 fication of vertebrate animals with which we are acquainted. In 

 saying this we have no intention of making a comparison of the 

 vertebrate and invertebrate sections to the disadvantage of the 

 latter — the greater complexity of the machinery of life in the Ver- 

 tebrata necessitates their being treated at greater length than 

 their invertebrate fellows, and this is especially the case when the 

 book to be written is intended especially for the use of students. 



This Manual is in fact, to a great extent, a treatise on the mor- 

 phology of animals. Pieferences to habits and mode of life are of 

 necessity cut down to the smallest possible dimensions ; but the 

 author carefully indicates the general distribution of the represen- 

 tatives of the various grou]»s in time and space, and of course some 



