ADVERTISEMENT. 



The present memoir by Professor E. A. Andrews, of the Johns Hopkins 

 University, on "The Young of the Crayfishes Astacus and Cambarus," forms 

 part of Volume XXXV of the Smithsonian Contributions to Knowledge. 



The memoir describes and illustrates the young of two kinds of crayfishes, 

 one from Oregon and one from Maryland, which represent the two most 

 diverse forms found in North America. Of these, one genus, found only in 

 North America, is widely distributed all over the United States, except the Pa- 

 cific Slope; while the other is restricted almost exclusively to the Pacific Slope 

 in North America, and at the same time it is almost the only genus in Europe 

 and Asia. This memoir fills a gap in the knowledge of these common animals 

 that still remained notwithstanding the extensive researches of Huxley and 

 many others. 



It determines the form and habits of the first, second, and third larval 

 stages ; gives the first detailed description and illustrations of the appendages 

 of the first and second stages; describes the hitherto unknown nature of suc- 

 cessive mechanical attachments of the offspring to the parent; and opens up 

 the problem of the nature and causes of the incipient family life in the cray- 

 fish. 



The new facts and comparisons add to the data for solution of the impor- 

 tant problems of the geographical distribution and the origin of the species 

 of crayfish, and they furnish a basis for practical application to the problems 

 of artificial culture and introduction of new kinds of crayfish. 



In accordance with the rule adopted by the Smithsonian Institution, the 

 work has been submitted for examination to a commission consisting of Dr. 

 Walter Faxon, of the Museum of Comparative Zoology, at Cambridge, Mas- 

 sachusetts; Prof. W. K. Brooks, of the Johns Hopkins University, and Prof. 

 W. P. Hay, of Howard University, who recommended its publication in the pres- 

 ent series. 



CHAS. D. WALCOTT, 



Secretary. 

 SMITHSONIAK INSTITUTION, 



WASHINGTON, June, 1907. 



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