No. 635] SHORTER ARTICLES AND DISCUSSION 



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tion of the river and are apparently impelled to seek out the 

 farthest limits of tidal water. 



Spawning takes place in April and continues until July in the 

 region studied. 



The factors influencing inland migration in the spring are sev- 

 eral. The temperature of the inland waters which is at that 

 time slightly higher than that of the ocean, and will later con- 

 tinue to increase, undoubtedly plays an important part. The 

 fresh water teeming with life and the salt marshes with myriads 

 of insect larvae, shrimps, and young fish furnish food for the 

 vigorous hungry fishes. The currents of fresh water have become 

 stronger and as the fish needs must react to a stream of water not 

 absolutely toxic to it, there is thus a pressun stimulus which 

 powerfully attracts. Of perhaps less importance is the fact that 

 the fresher waters when not too greatly contaminated by sewage 

 pollution are richer in oxygen. Certain it is that many fish not 

 anadromous come near the shore to spawn. Possibly the greater 

 metabolism incident to the development of eggs and sperm causes 

 them to seek out water which has a higher oxygen content. Roule 

 (1914) believes that salmon migrate to a richer supply of oxygen. 

 Wells (1915) has shown that starvation may cause certain fishes 

 to seek water of lower concentration of salts and other species 

 to behave in the opposite manner. 



Summer Habits 

 During the summer until early August there is continual mi- 

 gration inland with the tides, many of the fish returning to the 

 brackish water of rivers and creeks as the tide ebbs from the 

 marshes. Some few individuals of the species Fundidm hetero- 

 clitus find sanctuary in the marsh pools, and in all probability so 

 habituate themselves that they remain until cold weather. From 

 the three permanent pools not partially drained by ditches, col- 



