2 MR. E. VANSITTART NEALE [Jan. 8, 



as Sir I. Newton said of the attractive force of the earth, " htjpo- 

 theses non fingo." I appeal to a power which can be shown to be 

 at work in the present world ; I ask only, is it capable of explaining 

 the phsenomena observable now, or ascertained by probable induction 

 to have occurred formerly upon it ? 



These are great merits. But if these strong points of the theory 

 are connected with the principle of diversity, whence the animal and 

 vegetable creation derives the charm of its endless variety, it has, as 

 I conceive, also its weak points connected with the opposite principle 

 of unity : whence it attributes too large a share to death, and too 

 small a share to life, in the formation of species. 



In nature we find tivo powers at work, a principle of change pro- 

 ducing varieties, and a principle of permanence producing species. 

 Man is able, by making use of the principle of change, "adding up," 

 as Mr. Darwin happily says, the successive minute differences of dif- 

 ferent generations in different directions, to bring about wonderful 

 transformations in the original form whence he started, — from the Rock 

 Pigeon, for example, educing Carriers, Tumblers, Runts, Fantails, 

 &c., forms differing from each other more than do many undoubted 

 natural species — more, for instance, than Fieldfares differ from 

 Thrushes, or "Wood Wrens from Willow Wrens. But, although 

 man can do wonders through this principle of change, the principle 

 oi permanence slips through his fingers. He can preserve his varie- 

 ties in their distinctness, only so long as he intervenes to prevent 

 their interbreeding. Leave Carriers and Tumblers, Fantails and Runts 

 together, without pairing them, and a race will soon arise neither 

 Carrier, nor Tumbler, nor Fantail, nor Runt, but apparently in the 

 process of reverting towards the Rock Pigeon. But Fieldfares and 

 Thrushes, Wood Wrens and Willow Wrens live on for generation 

 after generation, side by side, and remain Fieldfares and Thrushes, 

 Wood Wrens and Willow Wrens still. 



That this is the case, is unquestionable. It is equally clear why 

 it is the case. Each distinct species in nature interbreeds by preference 

 with those of its own kind ; and if accidental unions do take place 

 between nearly allied species, the offspring are either sterile or, at all 

 events, much less fruitful than their parents. Here is the principle 

 of permanence in nature, preventing the principle of change from 

 producing confusion, as, again, the principle of change prevents the 

 principle of permanence from producing monotony. Whence comes 

 this principle of permanence ? I look to Mr. Darwin for an answer, in 

 vain. All that he says on this point amounts only to the position that 

 the progeny of nearly allied species are not always sterile. That the 

 preservatory tendency does not necessarily accompany a given amount 

 of external difference is clear ; for man can produce in living organisms 

 external differences greater than those associated in nature with this 

 principle of permanence, without calling that principle into action. 

 To attribute it to the greater length of time occupied in the formation 

 of natural species than in that of a variety, is to make an assumption 

 wholly destitute of proof, and indeed inconsistent with a very beau- 

 tiful and essential part of Mr. Darwin's hypothesis, namely, the doc- 



