206 W. C. ALLEE. 



region which occupied the summers of 1913-1921 inclusive. 

 The records given there show the distribution of the common 

 littoral invertebrates and discuss the relationships of the dif- 

 ferent animal associations present on the basis of their animal 

 components. 



The present paper deals with the results of an intensive study 

 of some of the localities considered in the preceding sections, 

 which was carried on in August and early September of 1920, 

 with some additional data from records taken the following 

 summer. In addition to considering the direct effects of different 

 types of bottom and shores, currents, tides and vegetation, this 

 study is particularly concerned with the possible correlation of 

 temperature, salinity, oxygen content and pH with the intertidal 

 and upper adtidal animal associations of the region immediately 

 around Woods Hole. 



Reference to the map published in connection with Study I. 

 of this series will give the general location of the region and the 

 Biological Survey 1 (pp. 170-190) gives a good account of the 

 general physiographie features. The more important of these 

 for the purpose of our discussion are: 



1. The whole region lies far back from the edge of the conti- 

 nental shelf. The 20 fathom line runs 10 miles off Martha's 

 Vineyard while the 100 fathom line, marking the edge of the 

 continental shelf, is 75 miles from Gayhead and about 90 miles 

 from Woods Hole. 



2. The unequal height of the tides in Buzzards Bay and 

 Vineyard Sound combined with the time difference of tides in 

 the two bodies cause strong currents to flow almost incessantly 

 from one to the other. All the localities discussed in this paper 

 are directly affected by these tidal currents except the wharf 

 pilings at Vineyard Haven and the bay at Gansett. 



3. There is a general westerly drift in the region so that the 

 Biological Survey estimates that all the water in Vineyard Sound 

 is renewed weekly and in Buzzards Bay in about double that time. 



4. The temperature is influenced by the Gulf Stream although 

 his is normally shut from shore by a wall of cold water. The 



water immediately around Woods Hole is warmer in summer 



: Sumner, Osburn and Cole: A Biological Survey of the Waters of Woods Hole 

 and Vicinity. Bui. Bur. Fish., Vol. 31. 



