402 THE INFLUENCE OF LIVING SUHEOUNDINGS. 



that the space enclosed within the ftinuel is divided perpendicu- 

 larly by a great number of septa into a corresponding number 

 of chambers. 



The new Myxicola of Port Mahon I found, as I have said, 

 among the polyps of Cladocora ; they lived in long mucilaginous 

 tubes which they had formed in the rifts in the coral, and in 

 which they could move about freely. As long as no light was 

 thrown upon them they protruded themselves just so far as that 

 the top rim of the corona of tentacles was on a level with the 

 tentacles of the polyps, so that when the worm and the polyps 

 were both extended the coral itself presented a perfectly level 

 surface of cups. Moreover, the funnels of the Myxicola were of 

 precisely the same chocolate-brown colour as the polyps ; and 

 when fully extended the interior of the funnel formed by 

 the tentacles looked exactly like the oral disc of one of the 

 neighbouring polyps, for the radial pinnules were in the same 

 position as those lines which, on the oral disc of the polyp, 

 radiate towards the narrow central oral slit; in the Myxicola 

 also a small central slit was observable, and all the parts which 

 corresponded so exactly in size and position also displayed 

 exactly the same colouring of greenish-gre)' with radial lines of 

 a lighter hue and a narrow white streak in the middle. In 

 short, the resemblance, in size, position, and colouring, of every 

 part of the two creatures was so perfect that for a long time I 

 took the corona of the Annelid for a polyp, until by an acciden- 

 tal blow I caused all the Myxicolfe of a large coral-stock to 

 shrink suddenly into their tubes, though it was not severe 

 enough to induce an equally rapid movement in the polyps of 

 the apathetic Cladocora. At the first moment I must confess 

 I felt an almost childish delight at having detected so flagrant 

 an instance of protective mimicry : here was a defenceless tube- 

 worm evidently most effectually pi'otected by its resemblance to 

 a polyp well defended by powerful weapons. 



However, I soon found reason to doubt this interpretation 

 of the facts ; why should the Annelid require any such protec- 

 tion, since it could withdraw itself with the swiftness of light- 

 ning into its tube imbedded in coral, where probably no enemy 

 would be able to follow it? Still, the wonderfully complete 



