NATURE 



241 



• A TREATISE ON ZOOLOGY. 

 Outlines of Zoology. By J. Arthur Thomson, M.A., 

 Lecturer on Zoology in the School of Medicine, Edin- 

 burgh. (Edinburgh and London ; Young J. Pentland, 

 1892.) 

 r^ENERAL. — The above-named volume of 604 pages 

 small octavo, the latest of Pentland's " Students' 

 Manuals," is divided into twenty-five chapters, with an 

 introduction and a well-constructed index. By way of 

 illustration, there are interleaved two-and-thirty sheets of 

 diagrammatic sketches. It is difficult to find upon 

 these any dozen figures which adequately represent any- 

 thing in nature, and the majority of the " diagrams " are 

 the rudest of rude sketch maps. Archetypes are well to 

 the fore with their misrepresentations and evil influences, 

 and such illustrations as those of the " unsegmented 

 worm," the " spinal canal" figure of Plate 22, and others 

 akin to them, are meaningless atrocities, conveying abso- 

 lutely no idea to the mind. The Peripatus series are 

 very suggestive ; they are three in number — namely, one 

 (bad) depicting the whole animal, another (worse) of a 

 nephridium, and a third (unfounded) representing a con- 

 ventional branched tube, spiral lining and all {sic). To 

 be brief, the illustrations are mostly bad, and might well be 

 dispensed with. Of those copied from well-known figures, 

 many are spoilt in the copying, while the remainder are 

 such as might have been produced in the greatest haste 

 by a person accustomed to reading about, but not to 

 handling, objects of the class delineated. 



The book itself is written in a clear and intelligible 

 style, and its author has been at immense pains in pro- 

 ducing it. He deals with marly difficult topics, especially 

 when they do not involve minute structural detail, with 

 conspicuous success. He is in some parts racy, in others 

 flippant, pace the remark (p. 264) that " even a wooden 

 leg may crumble before " the jaws of the termite ; and 

 he occasionally shows himself to be alive to difficulties 

 of the passing moment — for example, that of the histo- 

 genesis of the nerve fibre. Some sections of the work are 

 deplorably meagre, e.g. those devoted to the Ganoids, 

 Tunicata, Rotifera, and Sponges, and especially to the 

 Brachiopods and Polyzoa, which (following Lang) the 

 author ranks with the Sipunculids and Phoronis as the 

 " Prosopygii." Classifications such as that given of 

 the Chelonia, and the adoption of the absolutely ground- 

 less term " Ornithosauria" as the ordinal name for the 

 Pterodactyles, are bad examples of their kind. Akin to 

 the occasional flippancy already alluded to are the de- 

 scriptions of the embryonic membranes as " birth-robes," 

 of the crystalline lens and the liver as "moored "to ad- 

 jacent structures, and of the viscera as " swathed " in the 

 mesentery. All science worthy the name must be now 

 technical, whether set forth in the pages of a monograph 

 or of a text-book ; and when recognized terms are in daily 

 use they should be employed. Personal names are oc- 

 casionally mentioned ; and it is a curious detail that, 

 with one or two exceptions, those of workers in the 

 Edinburgh School are alone qualified. We strongly de- 

 precate the mention of individuals in an elementary text- 

 NO. I 1 85, VOL. 46] 



book, as unnecessary and liable to abuse ; but, in having 

 adopted the course alluded to, the author displays a be- 

 coming respect for his seniors, such as we could wish 

 were more general nowadays. His book is written 

 for Edinburgh students ; but we nevertheless note the 

 absence of all reference to certain organisms in vogue 

 among them — to wit, Trochosphccra, a knowledge of the 

 development of which was demanded in a recent syllabus 

 issued by authority. 



The book, however, while lacking in much that is of 

 primary importance, contains a bulk of excellent material. 

 It is wonderfully free of really gross errors, and we there- 

 fore willingly recommend it on its general merits as a 

 useful work of reference, believing that the author will 

 strengthen its weaknesses as opportunity occurs. 



The assertion that Limnocodium was "found in a 

 tank at Kew" will probably whet the appetite of that 

 estabhshment, and statements like that of the brain being 

 "but an anterior expansion of the medullary canal," while 

 self-explanatory, afford at least a relief to the reviewer. 



Analytical. — The author tells us in his preface that his 

 book is " intended to serve as a manual which students 

 of zoology may use in the lecture-room, museum, and 

 laboratory " ; and, in accordance with this, he subdivides 

 most of the chapters each into three sections, dealing 

 respectively with what we presume he would consider a 

 lecture equivalent, with the more didactic consideration 

 of type-structure, and with facts usually embodying the 

 principles of classification. A very ambitious scheme 

 this ; and it will be convenient to deal with each of the 

 three departments separately. 



First, as to the use of the book in the laboratory. 

 The author here deals with familiar types, and supple- 

 ments these here and there by the addition of wisely 

 chosen species. His descriptions are, however, at most 

 points insufficient and far too general, the one detailed 

 account being made to do duty in the case of the Simple 

 Ascidian (p. 358) for three distinct genera. This is not 

 as it should be. The method of laboratory instruction in 

 zoology employed in this country, with its rigid adherence 

 to the type-system, is, in the long run, but that of teach- 

 ing the alphabet whereby the student shall read ; and, even 

 were this not so, the laboratory training is one in discipline 

 and observation, wherefore it is of the highest importance 

 that any notes which shall be given the beginner for his 

 guidance in it, shall be rigidly confined to actual state- 

 ments of observed fact. The author partially disarms 

 criticism under this head by remarking that his book is 

 intended (preface) " as an accompaniment to several well- 

 known works," which he cites (p. 88), and among which he 

 enumerates leading laboratory treatises. Unfortunately, 

 however, the plan of construction of those works does 

 away with the necessity for his own as an adjunct to their 

 utility. And we have therefore but to deplore the in- 

 corporation of generalities and ambiguities, in a portion of 

 the author's treatise where they are calculated to en- 

 courage a general looseness, and to nullify much of the 

 good intended by the founders of the system which he has 

 adopted. 



On passing to the two remaining departments of the 

 book, we express ourselves at a loss to appreciate the 

 utility of a text-book in the lecture-room. Much that 



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