XV MEMOUJS OF THE CAliNEGIE MUSEUM 



Page. 



h. Origin of distribution 447 



4. Canibarus bartoni robiistiis 44!i 



a. Summary of facts 44!l 



b. Origin of distrii)uti<)n 44!i 



5. Cambarus carolinus 4 A 1 



<i. Summary of facts 4-")l 



I). Origin of distribution 452 



6. Cambarus monongalensis 4")-"5 



n. Summary of facts 45."! 



h. Origin of distrilnition 454 



7. C'ambarus diogenes 457 



(I. Summary of facts 457 



b. Origin of distribudoii 4511 



8. Summary of studies on distriliiitinn AiVl 



y . Life History 4of) 



1. Cambarus obscnrns 47<i 



2. Cambarus propinquus and C. j)ropinquus sanborni 47() 



3. Cambarus limosus 477 



4. Cambarus diogenes 4 Si) 



5. Cambarus bartoni and ('. bartoni robiistus 4S() 



6. Cambarus carolinus and monongalensis 4.S!» 



YI. Economic Yauue 4!)2 



1. Popular knowledge of crawfisbes 41t2 



2. Tbe use of crawiishes as food and bait 4!K) 



3. Crawfishes as scavengers ; their food ; their enemies 4!I4 



4. Crawfishes as obnoxious creatures 41)ii 



YII. BEARIXC4 OF THE ABOVE STUDIES OX THE ThEORV OF EVOTJTK IN "1!I7 



1. The Mutation-Theory of I)e Yries 41)S 



2. Species, Yarieties, and Yariations among the Pennsylvania Crawfishes 4iis 



3. Formation of S])ecies by Isolation, as exemplified by Pennsylvania Crawfishes, 504 



Bibliography 513 



Explanation of Plates 518 



