Ixxii 



the realm of science is thus shut off from that of common sense, 

 or that the mode of investigation which yields such wonderful 

 results to the scientific investigator is different in kind from that 

 which is employed for the commonest purposes of everyday 

 existence. " Common sense is science exactly in so far as it 

 fulfils the ideal of common sense, and science is simply common 

 sense at its best, that is, rigidly accurate in observation, and 

 merciless to fallacy in logic." Starting with this idea, the 

 Professor, with all that charm of language and lucid exposition of 

 which he is so consummate a master, proceeds to display the 

 natural history of Astacus fliiviatilis , the common crayfish of 

 our rivers, then to enquire into its morphology and physiology, 

 and finally to examine into the distribution* and wdiat he terms 

 " the crown of biological effort," the setiology of this group of 

 animals. And the reader is thus shown how the careful study of 

 one of the commonest and most insignificant of creatures leads 

 step by step from everyday knowdedge to the most difficult 

 problems of Zoology and the widest generalizations of Biological 

 Science. 



Meanwhile our colleagues have not been idle. Mr. Owen 

 Wilson has issued the two concluding parts of his illustrations of 

 ' Larvse of the British Lepidoptera '; Mr. Herbert Goss has 

 continued his admirable papers, ' On Fossil Insects and the 

 British and Foreign Formations in which Insect Remains have 

 been detected ' ; Mr. M'Lachlan has produced the eighth and 

 penultimate part of his 'Monographic Revision and Synopsis of 

 the Trichoptera of the European Fauna,' containing the family 

 Rhyacojjliilida ; and Messrs. Godman and Salvin have issued the 

 first two parts of the zoological portion of their * Contributions to 

 the knowledge of the Fauna and Flora of Mexico and Central 

 America', a magnificent quarto, to be published in parts at 

 intervals of a couple of months, and estimated to extend to not 

 less than sixty parts of Zoology, to be followed by an introductory 

 volume wherein the physical features of the country will be 

 described and illustrated with maps. The region from which 

 contributions are to be levied includes the whole of Mexico from 



* Crayfishes do not inhabit every British river; and Prof. Huxley says (p. 288) 

 that he cannot hear of any, for example, in the Cam or the Ouse on the east, or in 

 the rivers of Lancashire and Cheshire on the west. Unless my memory deceives 

 me as to the occurrences oi five-aud-thirty years ago, there were then crayfish in 

 the Little Ouse, near Brandon. 



