42 BY THE DEEP SEA. 



I hope that in the foregoing remarks I have made it quite 

 clear that our Sea-oak Coralline is not an individual but a 

 community of individuals a community on the strictest of 

 co-operative principles, in which the good fortune accruing to 

 one of the polypites by food falling in its way, is shared by 

 all alike ; for a polypite cannot digest it and retain it to its 

 own selfish use, instead, it goes to the nutriment of the common- 

 wealth. 



Some of these Hydroid Zoophytes, though sharing the com- 

 munist character, are much simpler in form, and we shall find 

 a common example ready to our hand on almost anything in 

 the way of stone or shell removed from a rock-pool. It is a 

 minute creature, as stout as a " short white " pin, and about 

 a third of the length, white or pinkish ; a number of them 

 spring in a row from a creeping stem of firmer substance, in 

 which are well-defined tubular openings, in which the upright 

 bodies stand. These answer to the calycles of Sertularia, just 

 as the upright bodies agree with the polypites of that genus. 

 The name of this creature is Clava mnlticornis^ and it may 

 conveniently be called the Many-horned Club. It gets its 

 name Clava from the shape of the polypite which thickens 

 towards the top, and then tapers off again to the summit, 

 whejre its mouth is situated. It has a number of tentacles, 

 varying from ten to forty, according to age, but these do not 

 form a regularly-disposed crown round the mouth ; instead, 

 they are placed anyhow on the thickened part of the polypite. 

 The name multicornis refers to these many-horns or tentacles. 

 An advance on this type is seen in Coryne pusilla, a much 

 larger but equally common inhabitant of our rock-pools, in 

 which the tentacles are knobbed, and are arranged in a series 

 of more definite whorls. 



There is another group which is more likely to be confounded 

 with the Sertularians by those who are content with hasty 

 glances at things ; but species of the one group may be readily 

 distinguished from the other by the aid of a simple lens. 



