i8o Wild Life in Wales 



of ivy, or to the roots of a tree pendulous from an over- 

 hanging bank. 



It is not often, perhaps, that the schoolboy, when regard- 

 ing the turquoise gems which he has rifled from such a 

 nest, pauses to consider that their blue shells are, in chemical 

 composition, almost identical with the grey limestone he is 

 treading under foot, or with the black, or white, bone, 

 or ivory, haft of his pocket-knife. Nay, more, that his 

 sister's mother-of-pearl brooch, or even a pearl itself, or 

 the lump of red coral which adorns the mantelpiece at 

 home, as well as the marble of which the mantelpiece is 

 made, are composed of one and the same substance, 

 namely, carbonate of lime, with the addition of a little 

 magnesia, phosphates, or other matter. Yet the more 

 often such facts are impressed upon him the better, and 

 it is in the hope that some youthful reader may peruse 

 these lines that I recall them here. The same subtle 

 agencies that are ever at work within our own bodies, 

 extracting calcium from the air we breathe and from the 

 food and water we consume, in order to build up our 

 own bony skeleton, are as actively engaged in the snail, 

 or the bird, in secreting the substance that goes to form 

 their shells. Just as assiduously do the coral animalculae 

 collect calcium from the water of the ocean, and, leaving 

 it in their minute skeletons, in the course of ages build up 

 the coral reef that in time supports an island, and becomes 

 inhabited by plants, insects, reptiles, birds, 1 and in time, 



1 Plants undoubtedly preceded animals in the first colonisation of the Earth, 

 plants being the producers and animals the consumers ; the former, only, 

 having the power to convert into organic matter the primitive elements con- 

 tained in rocks or soil, and all the higher animals deriving their sustenance 

 either directly from plants or indirectly by preying upon other creatures whose 

 tissues have already been built up from vegetable food ; but it must not on 

 that account be too hastily assumed that the occupation of all new territory 

 necessarily follows in the order here set down. In many cases it is known 

 that it is not so, birds being frequently, perhaps generally, the first arrivals. 

 In describing some of the islands of the Atlantic, where no plant not even a 

 lichen was to be found, and where the only terrestrial animals were sea- 

 birds, and a few insects which lived either upon them, their feathers, or their 

 dung, and spiders which preyed upon the latter, Darwin wrote : " The often 

 repeated description of the stately palm and other noble tropical plants, 

 then birds, and lastly man, taking possession of the coral islets as soon as 

 formed, is probably not quite correct ; I fear it destroys the poetry of this 



