16 



LIFE BY THE SEASHORE. 



which is adapted for life in mud must be confined to areas 

 where mud-beds occur, and thus be absent from long 

 stretches of shore. But apart from simple cases of this 

 kind, it often happens that an animal whose adaptation 

 to some special condition of life is not very obvious, is yet 

 confined to certain localities, and is absent from intervening 

 places which are apparently equally suitable. Thus the 

 beautiful Alcyonium (Dead Men's Fingers) only occurs 

 sporadically between tide marks, probably in part because 



it offers little resistance 

 to wave action, and re- 

 quires peculiarly shel- 

 tered spots for fixation. 

 Again, the Plumose 

 anemone (Actinolola 

 dianthus, Fig. 26, p. 73), 

 one of the finest of our 

 British anemones, is on 

 the East Coast at least 

 a very local form, some- 

 times occurring in great 

 beauty and profusion in 

 one particular spot only 

 in a large bay. Many 

 other examples might 

 be given, but without 

 labouring the point, we 

 may say generally that 

 although it is an advan- 

 tage for .adult shore 

 animals to be firmly 

 fixed, or to be able to offer passive resistance of some sort 

 to wave action, yet it is also highly desirable that they 

 should at some period of life possess sufficient power of 

 movement to enable the species to be carried to fresh 

 localities, and suitable localities may be a considerable 

 distance away from the home of the parents. In point 

 of fact, almost all shore animals produce minute active 

 young, which usually live near the surface, and are eminently 

 well adapted for transport by currents or by their own 

 activity. One of the most interesting subjects of study 



Fio. 5. Dead Men's Fingers (Alcyonium digi- 

 tatum), a colony of small polypes. 



