CCELEXTERATES. 



33 



budding takes place in a different manner from that of the massive forms 

 and the result is a branched condition. Our figure shows a portion of 

 one of these corals, all over which may be seen little prominences or 

 tubes, each of which was in life occupied 

 by a polyp not essentially different from 

 a sea-anemone or from the polyps form- 

 ing the Astrcea, and yet how different the 

 result ! 



The mode of growth of one of these 

 corals is interesting. At first there hatched 

 from the egg a single polyp, which settled 

 down and began its secretion of carbonate 

 of lime, especially at its base. A bud was 

 soon formed, and this followed the example 

 of its parent. As the secretion of lime went 

 on, each polyp was forced upwards in its 

 tube, leaving behind a solid calcareous mass. 

 As they grew their courses diverged, and 

 each kept on budding, until at last each 

 original bud was the parent of a branch, 

 from which other branches arose in a simi- 

 lar manner. In every branch, therefore, the 

 terminal polyp is to be regarded as the 

 parent of the branch. 



In all the sea-anemones and corals so 

 far mentioned the primary number of par- 

 titions is six. To this group, with this 

 mathematical basis, the name Actinaria is 

 given, — a name derived from the generic 

 name of one of the European anemones, 

 Actinia. There is another group of coral- 

 producing polyps, in which, as will be 

 seen from the cuts introduced, eight is 

 the ruling number. Thus each has eight fig. 35. — a branch of deer's-hern coral 



tanfinlAc A i (Madrepora). Below, a magnified sec- 



lenidCieS ; and, were We to examine the m- tion, showing the cavities occupied by the 



teraal structure, the same number would P ° lyps ' 



be found to prevail throughout the organism. The name applied to this 



group is Alcyonaria, and its origin is interesting. 



Among the ancients the alcyon. or, better, halcyon, enjoyed a high 

 repute. It built its nest in the winter, and at that time the sea was 

 always calm. The old story still survives in our "halcyon clays." The 





