334 Zoological Society : — 



By this conception of the origin of species, we escape from another 

 serious difficulty, which appears to me to lie in the way of the con- 

 ception of their formation by such a process of external selection as 

 Mr. Darwin assumes. "When we are asked to suppose that differ- 

 ences so considerable as we observe between diflFerent organisms, past 

 or present, have been brought about by a process precisely analogous 

 to that by which man can change the shape of a sheep or a pigeon, 

 we naturally ask whether there are no limits to the amount of change 

 producible by man ? Could he, by any degree of watchfulness how- 

 ever long continued, expand a race of sparrows to the size of condors, 

 or condense a race of turkeys to the size of humming-birds, or 

 lengthen out a pig's snout, and thicken his legs and body into a trunk 

 and frame similar in size to the elephant ? Mr. Darwin must contend 

 that this would be possible, if man continued to act uninterruptedly 

 for a sufficient length of time in the same direction. Perhaps future 

 experiments may enable us to speak with certainty upon this point. 

 At present I conceive the general feeling of the most experienced 

 breeders would be against him. It may be true that they " habitu- 

 ally speak of an animal's organization as something quite plastic, 

 which they can mould almost as they please " by the principle of 

 selection (Darwin, p. 31). Yet Mr. Darwin also tells us that "all the 

 breeders of the various domestic animals, and cultivators of plants, 

 with whom he has ever conversed, or whose treatises he has read, are 

 firmly convinced that the several breeds to which they have attended 

 are descended from so many aboriginally distinct species " {id. p. 28). 

 Now they are no doubt mistaken in this notion ; and it is easy to see 

 whence the mistake has arisen, — namely, from each one having 

 attended only to one out of many possible kinds of variation pro- 

 ducible in the particular animal or plant forming the object of his care. 

 But it is difficult to conceive whence the general notion coidd be 

 derived, if each breeder found no limit, no stop, to the amount of 

 variation which he can produce in the particular direction selected by 

 him for experiment. 



But this difficulty disappears, hke that first stated, if th<e process 

 of selection be transferred from the external action of circumstance, to 

 the internal action of the living Power gradually modifying the con- 

 stitution of the individual. It is a supposition agreeable to common 

 experience, that to each particular constitution certain limits of 

 change are assigned, within which the possible varieties of the creature 

 possessing it fluctuate. But if the constitution changes, these hmits 

 must be presumed to change also. Each fresh species, then, may be 

 regarded as a resting-place in the advance of life, — the development 

 of the possible varieties inherent in it being left to the external action 

 of circumstances; while among these the Power manifested in life 

 selects the forms most suitable to be converted into other species, and 

 thus carries on the differentiation of Uving beings a step further in its 

 proposed course. 



Other grave difficulties disappear if we accept the idea of " typical " 

 in place of "natural" selection. One very serious one, in my judg- 

 ment, is the difficulty of seeing how natural varieties could perpetuate 



