Bihliographical Notices. 55 fi cation occupies a very humble place amoug biological efforts and that all systems must of necessity be tentative and temporary, soon to be superseded by others, the results of a larger knowledge gained by the contemplation of a wider horizon." Thus the reader must not expect to find any more in this respect than exists in the table of " Coutents " at the commencement of the ' Monograph.' Still, after some suggestions towards the attainment of this object, the author states that " there is no more hopeful field of labour for a young naturalist seeking for ' new worlds to conquer ' than that provided by the Freshwater Sponges." Truly there is much yet to be done in spongology generally, both specifically and physiologically, towards classification before it can be put on a par with botany in these respects ; but who can expect this to be otherwise with a science that is hardly a century old ? The text is accompanied by twelve plates, the numerous repre-sentations in which, with copious explanations, are, in point of exactness, in keeping Avith all that has preceded. They are not on the scale which commands attention from its great size (that is, like the figures over a caravan at a country fair), but, on the contrar}', so small and unpretending as almost to require a lens for the examina-tion of their detail, whose minuteness and truthfulness to nature will then be found to present objects of much admiration. ^^'e congratulate Mr. Potts on having produced a ' Monograph ' which is characterized throughout by modesty, ability, and, pre-eminently, practical utility. A Manual of Zoologn for the Use of Students, ivitli a General Intro-duction on the Principles of Zoology. Ey Henry Alletne Nicholson, M.D. &c. Seventh Edition, rewritten and enlarged. 8vo. Blackwood : Edinburgh and London, 1887. We have had occasion so frequently to call attention to the publi-cation of successive editions of this ' Manual,' that it would be hardly necessary to do more than to notice its reappearance, were it not that the author has made so many additions and alterations in the present edition as to place the book upon a new footing. It is, as announced on its titlepage, to a great extent rewritten, and is very considerably enlarged ; and an examination of the contents will show that the author's labours have not been thrown away, as the book is a very great improvement upon its predecessors. Of course the general treatment of the subject is the same as before, and the work is cast in the same shape ; but throughout we find evidence of the influence of the most recent additions to the literature of scientific zoology. This is marked not only in the systematic portion of the book, but also in the general introduction, in which the author has touched, briefly indeed, upon all the more important points which have come to the front of late ) ears, espe-
A manual of zoology for the use of students, with a general introduction on the principles of zoology. By Henry Alleyne Nicholson, M.D. &c. Seventh Edition, rewritten and enlarged. 8vo. Blackwood : Edinburgh and London, 1887
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