STUDIES IN MARINE ECOLOGY. 207 



and probably cooler in winter than outlying waters. 1 The 

 Biological Survey reports an annual temperature range of 25 C. 

 at the Fish Commission pier where the water is much mixed by 

 the current through the Hole. The range is greater in stagnant 

 water such as that in Blind Gutter at Lackey's Bay where the 

 annual range is over 33 C. 2 



5. The intertidal zone is comparatively narrow, being more 

 extensive in Buzzards Bay than in Vineyard Sound. 



6. The shores of the region are usually lined with rocks which 

 extend well below the low tide level and give way there to sandy 

 bottoms in the more exposed places. In sheltered regions mud 

 of organic origin is deposited over the sand. 



7. The Biological Survey found that the salinity of Buzzards 

 Bay averaged 3.00 per cent.; that of Vineyard Sound, 3.075 

 per cent. The open Atlantic runs to 3.6 per cent, or more. 3 



During the investigation the open water was sampled in four 

 inshore localities: 4 Off the Buzzards Bay entrance to N. W. 

 Gutter (Map, No. 10), in the Hole at Woods Hole; in Vineyard 

 Sound at the entrance to Lackey's Bay (Map, No. 6) and at the 

 entrance to Gansett Bay (Map, No. 11). 



The wharf pilings were studied at Crane's Wharf (Map, No. 5) 

 near the steamboat wharf in Woods Hole and at the old steam- 

 boat wharf in Vineyard Haven (Map, No. 1). The rocks at 

 Northwest Gutter near its Bay entrance (Map, No. 10), in 

 Lackey's Bay at the entrance to Blind Gutter Flats (Map, No. 6) 

 and at Gansett. The associations of the flats were studied at 

 Northwest and Blind Gutters and at Gansett, together with 

 some observations in the creek leading to Southwest Gutter. 

 In all 122 sets of collections were made. 



These localities were chosen for intensive study because they 

 are typical of the region and because of their proximity to and 

 ease of access from the laboratory. 



1 Cf. discussion in Biological Survey, pp. 37 and 50. 



2 Water over the eel grass in Lackey's Bay had a temperature of 32 deg. C. on 

 the afternoon of August 15, 1920. There is no reason to suppose that this tempera- 

 ture is unusual. In winter the temperature must frequently fall below the freezing 

 point of sea water. 



3 See Murray and Hjort. 



1 For descriptions of the different habitats see Study I. of this series. 



