156 THE STORY OF LIFE IN THE SEAS. 



their food is derived entirely from the water 

 that surrounds the Coral and not any portion 

 of it from the cells or tissues of the Coral-polyps 

 themselves. 



There is a great deal of difference in the 

 Millepores from one and the same coral reef, 

 in the extent to which the Barnacles have 

 attacked them. In some specimens large areas 

 of the Coral are beset with the little holes, in 

 others only one or two may be found on the 

 whole colony, whilst others again are quite free 

 from them. Now when we compare carefully 

 the anatomy of those Millepores with the 

 Barnacles and those without them, no single 

 sign or symptom can be found that the vigour 

 or strength of the former is in any way im- 

 paired. If then there is no evidence that the 

 Barnacles are parasitic, in the sense that they 

 are injurious to the Millepores, we must next 

 inquire whether they could possibly be of any 

 service to them. 



The polyps of the Millepores feed after the 

 manner of the polyps of other Corals, upon 

 minute organisms floating in the sea ; these they 

 paralyse and capture by means of tentacles bear- 

 ing stinging cells. The food is in the ordinary 

 course brought within reach of the tentacles 

 by the tides that sweep over the reefs. The 

 Barnacles also feed upon minute organisms of 

 the same kind, but they are provided with six 

 pairs of long feathery legs which by a curious 

 vibratory movement create currents in the water. 

 When there are many Barnacles in close proxi- 

 mity to one another it is quite probable that the 



