22 THE STORY OF ANIMAL LIFE 



does not project beyond the later-formed coils, 

 and the whole shell has a rounded outline. This 

 little creature lives on the long seaweeds which 

 grow at low-water mark or near it; and when the 

 sea is rough it is obviously liable to be dashed 

 from its foothold on the seaweed and flung vio- 

 lently down, as the huge seaweeds sway about in 

 the shallow waves. We may easily satisfy our- 

 selves that this is an accident that frequently 

 happens, by examining the shore when the tide is 

 going out, on some stormy spring or autumn 

 day. Numbers of the yellow periwinkles are then 

 to be found crawling on the sand, and striving to 

 regain their place in the seaweedy rocks as soon 

 as possible. On a calm day you will rarely see 

 one crawling on sand above low-water mark, for 

 it is a place they do not choose by preference; 

 those that are to be found there on the stormy 

 day have lost their foothold, and have been 

 washed about by the tide. Had they, like some 

 other kinds of periwinkle, a sharp spire, how many 

 would be the casualties under these circum- 

 stances! But as it is, you do not see a single 

 specimen with a broken top : the rounded spire 

 is an adaptation to circumstances, required for 

 the protection of the tenant of the shell. (See 

 Fig. 2.) 



It may be added that the yellow Periwinkle is 

 not only protected from mechanical sources of 

 danger by its form, but is also in some degree 

 protected from living enemies by its colour. This, 

 at first sight, seems exceedingly conspicuous. We 

 must remember, however, that the animal often 

 lives in that part of the shore where the Bladder 

 Seaweeds, or Fuci, are extremely abundant. 

 The flowering ends of these are of a yellow 



