NO. 48. — 1897.] ON WALLACE'S THEORY. 



81 



and south confines, would describe them as separate species ; 

 whereas if he took a walk through the wood and collected 

 individuals from all parts, he would find that there was 

 every gradation between the extreme forms. Let us now 

 suppose that some change comes over the environment, so 

 that all the varieties in the centre of the wood become 

 extinct, then the north and south varieties become species. 

 I consider this ought to be called " Wallace's theory." He 

 propounded it simultaneously with Darwin, who, as we all 

 know, became dissatisfied with its sufficiency ; and since his 

 day all kinds of modifications of the theory have been pro- 

 posed, Wallace alone standing firmly by the original idea. 



When standing on a coral reef one is astonished at the 

 extraordinary divergences under simultaneous conditions. 

 On the sandy floors of the shallow sunlit pools we find 

 sea-cucumbers, starfish, various kinds of molluscs, beautiful 

 annelids, whilst darting through the water numerous 

 brilliantly coloured fish of widely different families 

 are seen swimming about. There is no apparent struggle 

 for life : all seems peace and harmony, an abundant supply 

 of well aerated water is furnished by the breakers outside, 

 whilst the coral polyps themselves, and an abundance 

 of minute life in the water and the sand, supplemented no 

 doubt by the eggs or very young forms of the different 

 inhabitants, furnish food for all ; only the brilliantly 

 coloured little crabs seek refuge in the interstices of the 

 coral, or attach sponges or weeds to their shells until they 

 become indistinguishable from their surroundings. It is 

 curious that the best protected and best armed group should 

 be the most retiring. This probably arises from the 

 periodical casting of the shell, which leaves their soft bodies 

 the favourite prey of their own species — at least this is 

 known to be the case with the lobster. How could these 

 great divergences ever have arisen ? There seems no point 

 of vantage from which Natural Selection could commence 

 its operations. 



16—97 G 



