SOME ANIMAL ARCHITECTS. 149 



North Sea and Atlantic, have been inundated. It is need- 

 less to point out that no such evidence is forthcoming, and 

 that we are dealing with a subsidence of land, and not with 

 a rising of the sea. Ample evidence of the existence of 

 large areas of land-subsidence is afforded by the geological 

 survey of the southern coasts of Sweden ; the lower streets 

 of the seaport towns of Scania, formerly inhabited, being 

 now under water. The coasts of Greenland are similarly 

 being depressed, and very marked alterations in climate 

 may be shown to result from the existence of these move- 

 ments on the part of what can no longer be regarded as the 

 " stable land." 



Bearing in mind the fact that land may subside com- 

 pletely beneath the surface of the sea, we may return from 

 this necessary digression to the consideration of Mr. Darwin's 

 theory of coral-reefs. Beginning with the fringing reef, well 

 seen in the island of Mauritius, it is shown that such an 

 erection forms the initial stage of coral-formation. Here we 

 find a natural foundation for the work of the living coral- 

 polypes ; the animals having fixed upon a natural coast-line, 

 and having, at a suitable depth for themselves, constructed a 

 belt or fringe of coral, the seaward depth of which, as we 

 have seen, does not descend below the fifteen-fathom line. 

 So long as the land skirted by the fringing reef remains stable 

 and stationary, so long will the reef remain essentially in its 

 primitive condition. According as the shore slopes abruptly 

 or gently, so will the breadth of the reef be limited, or be 

 extended out to sea. No increase in depth is possible, 

 seeing that the polypes have already attained, or have built 

 upwards from, their lowest depth ; and if the land remains in 

 the condition in which it was when the fringing reef was 

 first formed, the latter erection will also remain -in statu 

 quo. But, in accordance with the evidence of the geologist, 

 land may sink. If we suppose that the land on which a 

 fringing reef has grown slowly subsides, changes of great 

 extent may be shown to occur within the attached zone of 

 coral life. The lowermost corals, being carried out of their 



