THE CRAYFISH: 



AN INTEODUCTION TO THE STUDY OP ZOOLOGY. 



CHAPTEE I. 



THE MATUEAL HISTORY OF THE COMMON CEATEISH 

 (_Astacus fluviatilis.') 



Many persons seem to believe that what is termed 

 Science is of a widely different natm-e from ordinary 

 knowledge, and that the methods by which scientific 

 truths are ascertained involve mental operations of a 

 recondite and mysterious nature, comprehensible only by 

 the initiated, and as distinct in their character as in 

 their subject matter, from the processes by which we 

 discriminate between fact and fancy in ordinary life. 



But any one who looks into the matter attentively will 

 soon perceive that there is no solid foundation for the 

 belief that 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 inves- 

 tigator, is different in kind from that which is employed 



