108 



under "started" bark, and Polygyra albolahris haunts holes and 

 large crevices in dry weather. 



Fluviatile Species. 



Found in all varieties of habitat. 

 Physa gyrina. 



In large summer-dry ponds. 

 Physa gyrina, Planorhis trivolvis, Plaiiorbis parz'us, Planor- 

 bis exaciwiis, Segmentina armigera, Musculium partumeium, 

 Ancylus parallelus, Lymnaca reflexa. 



In small pools of very transient character. 

 Lynmaea caperata, Aplexa hypnorum, S phaerium occidentale. 



In the river, which does not run dry. 

 Sphaerhim stamincum, Musculium transversiim, Lampsilis, 

 Anodonta, Anodontoidcs, Physa gyrina, Planorhis trivolvis, 

 Ancylus rivularis. 



Semiaquatic ; on the edge of river and pools. 

 Lymnaea parva sterkii. 



In brooks and overflow from river. 

 Lynmaea caperata. 



C. W. Andreivs. — "Is Skokie Marsh connected with the outer 

 belt area in Qiicago?" 

 F. C. Baker.— "It is." 



Victor E. Shelford presented an illustrated paper of which an 

 abstract is given below. 



ECOLOGICAL SUCCESSSION OF FISH AND ITS BEAR- 

 ING ON FISH CULTURE. 



The investigation with which my paper deals is not yet com- 

 pleted. The results are too extensive for reading before the 

 Academy. Accordingly, only an abstract of the chief facts and 

 conclusions is given here. The completed work will be 

 published elsewhere later. 



I. DeI'Inition. Ecological succession differs from geologi- 



