PROTRACTILE MOUTHS 



and easier to see. These holes allow entrance to the water 

 which passes through them into a series of canals and 

 chambers by which the whole of the creature's interior 

 is traversed. There it continually circulates, entering 

 in one place and going out in another, ceaselessly being 

 renewed. This persistent imbibition, or perhaps we 

 should say incessant irrigation, that goes on within 

 the creature, brings to the sponge the substances it 

 needs for breathing and feeding. The water contains 

 oxygen in solution, and food particles in suspension, 

 takes them along with it to the interior of the organism, 

 passes them over to the living tissues; then flows away 

 and gives place to other water, which carries on the 

 action. This ceaseless renewing produces the required 

 result. 



Near the sponges, like them resting on fragments of 

 rock, are the sea-anemones. These are more impression- 

 able, less inert, and there is no room for doubt that they 

 are animals. Their body is cylindrical, contractile, 

 elastic, and stands up like a column well settled on its 

 base. Sometimes it rises vertically and spreads out at 

 the top; sometimes it contracts into a dome-shaped 

 mass. The summit has tentacles gathered into a crown 

 and surrounding a spacious mouth opening into a large 

 stomach, the cavity of which occupies most of the 

 animal's interior. When we come to consider it, the 

 sea-anemone is little more than a stomach fitted with 

 tentacles. 



It is a curious sight. It cannot shift its position; it 

 is fastened to the place in which it lives; its tentacles 

 move, showing that it is possessed of reasonably acute 

 senses. Sometimes they spread out uniformly, turning 

 themselves outwards; sometimes they fall back inwards. 

 Some of them lengthen, some shorten; they are almost 

 incessantly on the move. The creature has the added 

 attraction of exquisite, sometimes intense, coloration, 

 the colours varying according to the species, brown, 

 green, yellow, red, steel or spotted. It is not hard to 



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