354 



NATURE 



{Feb. 12, 1880 



field of labour ; in relation to the human mind nature is 

 boundless ; and though nowhere inaccessible, she is 

 everywhere unfathomable." 



It is, then, with the object of arriving at a satisfactory 

 conclusion as to the crayfish's place in nature, and to 

 educe from the study of it such conclusions as may tend 

 to throw light on the place in nature of other living things, 

 that the reader is supposed to enter upon the considera- 

 tion of the facts which Prof. Huxley lays before him. 



No pains have been spared in the illustration of the 

 text — the woodcuts (eighty-one in number) reflecting 

 great credit both on the artist for his skill, and on the 

 publisher for his enterprise. We have, after a general 

 disquisition on the natural history of the crayfish (by no 

 means the least interesting in the book), two devoted to 



Astacus lcJ>todaclylus (after Rathke, 3 nat. size). 



the consideration of the crayfish as a mechanism — in fact 

 its physiology. Here a good deal of the anatomy is given 

 and considered from the point of view involved in the 

 question " What does it do ? " Then we have the morpho- 

 logy of the English crayfish — the structure and develop- 

 ment of the individual minutely set forth, even each joint 

 of each leg, and each tuft on each gill, and each group of 

 hairs, being described and figured. We are enabled by 

 the courtesy of the publishers to reproduce one of these 

 highly-finished engravings representing the most fully- 

 developed of the crayfish's limbs (Fig. 1), and some others 

 which give a fair notion of the excellence of the illustra- 

 tions of Prof. Huxley's book. 



To this follows a chapter in which the English cray- 

 fish is compared in a variety of points with crayfishes 

 of other lands, such as those of Russia (Fig. 2), of 

 Australia (Fig. 3), and of North America (Fig. 4), 



with lobsters and prawns, and it is explained how 

 the amount of likeness and difference between these 

 various but closely similar animals may be expressed by 

 the method of classification in groups. Finally we have 

 a chapter on the geographical distribution of crayfishes, 

 and the facts therein narrated, together with those ad- 

 duced in the previous chapter, enable the author to sketch 

 the probable pedigree of crayfishes, that is, to refer them 

 to their causes, viz., to the action of such physical agencies 

 as flowing rivers, land and climatic barriers, brought to 

 bear upon successive generations of the offspring of 

 marine lobster-like ancestors which had a wide distribu- 

 tion in the earlier tertiary and later mesozoic periods, and 

 before taking to fluviatile life had separated into two dis- 



Fig. 3. — Australian Crayfish (J nat 



tinct races characterised by differences of form, the one 

 giving rise to the crayfish of the northern hemisphere (the 

 Potamobiidae), and the other to the crayfishes of the 

 southern hemisphere (the Parastacida;). 



The novel portion of this book (novel at least to 

 those who do not study the transactions of learned 

 societies) is that in which Prof. Huxley details the very 

 interesting results which he has obtained by a minute 

 examination of the gills attached to the bases of the legs 

 and sides of the body in all crayfish and allied forms. 

 Three series of these gill-plumes may be distinguished 

 according as they are attached to the leg, to the joint- 

 membrane, or to the side of the body (Fig. 5). An ideally 

 perfect crayfish would have all three series complete on 

 each ring of the body in the branchial region (including the 

 region occupied by the three pairs of maxillipedes and 



