76 WONDERS OF ORGANIC LIFE. 



secrete large calcareous masses for its support, 

 with polype cells variously arranged. In these 

 instances the calcareous support is firmly con- 

 solidated to the rock on which it is based, and 

 the polypes, often of most beautiful tints, resem- 

 ble thickly-scattered flowers on a glistening 

 bank ; as examples in point we mention Astrcea, 

 Meandrina, etc. 



It not unfrequently occurs, that the axis, or 

 skeleton, invested by gelatine is not firm and 

 calcareous, but horny and elastic ; in this case 

 it is generally in the form of a leaf, or fan, or 

 it resembles the branch of a weeping willow, 

 and, rooted on the rock, bends to the waves. 

 In these instances there are not always polype 

 cells in the substance of the horny stems or 

 twigs, but the cells are placed in the gelatinous 

 bark, or cortical substance, investing the stem 

 and twigs, and within these cells the polypes or 

 animal flowerets dwell. In some forms, as in 

 Iris hippuris, the stem is composed alternately 

 of joints of flexible horny matter, and of beads 

 of white calcareous matter, the whole being 

 invested by a gelatinous bark of considerable 

 thickness, in which the polype cells appear like 

 numerous pits or dimples. 



In the cases cited above, the living gelatine 

 secretes or deposits an internal solid substance, 

 as the inner bark of a tree secretes the wood, 

 which is the common mechanical support of 

 the whole. But we must now reverse the 

 picture, and imagine a number of polypes 

 united by thread-like films into one being, these 



