598 A NATURALIST ON THE " CHALLENGER." 



occurred which has resulted in the various forms of animal and 

 vegetable life. 



On the theory of evolution, it is impossible that plants or 

 animals of any advanced complexity, at all resembling those 

 existing on the earth, should exist on other planets or in other 

 solar systems. It is conceivable that very low forms of vegetable 

 life may exist on other planets and may have been by some 

 means trans23orted to the earth : the idea is conceivable, though 

 highly improbable. But it is quite impossible that that infinitely 

 complex series of circumstances which on the earth has conspired 

 to produce from the lowest living forms a Crustacean for example, 

 should have occurred elsewhere ; still less is it possible that a 

 bird or a Mammal should exist elsewhere ; still more impossible 

 again that there should be elsewhere a monkey or a man. 



All these forms are quite certainly terrestrial, and terrestrial 

 only, as surely as is the Apteryx a peculiar development of 

 New Zealand alone, or the Dodo a production of the Mascarene 

 Islands only. It is even probable that protoplasm, itself, the 

 basis of all life, is a production entirely confined to our small 

 planet. 



That the " Challenger " Expedition has been a great scientific 

 success has been fully acknowledged, and all praise is due to the 

 Government which promoted it, and to the present Government 

 which has supplied funds for the publication of the results. 

 The highest praise is, however, due to those naturalists, especially 

 Sir Wyville Thomson and Dr. Carpenter, who, by their energy 

 and perseverance, actually originated the Expedition. 



With regard to any future scientific expeditions, it would, 

 however, be well to bear in mind that the deep sea, its physical 

 features and its fauna, will remain for an indefinite period in 

 the condition in which they now exist and as they have existed 

 for ages past, with little or no change, to be investigated at leisure 

 at any future time. On the surface of the earth, however, 

 animals and plants and races of men are perishing rapidly day 

 by day, and will soon be, like the Dodo, things of the past. 

 The history of these things once gone can never be recovered, 

 but must remain for ever a gap in the knowledge of mankind. 



The loss will be most deeply felt in the province of Anthro- 



