7590 Noliccs of New Books. 



animal's ancestors, would point to a former more perfect condition of 

 the now absorbed organ. 



The next class of evidence Mr. Darwin dwells upon relates to the 

 assumed processes of change by which the conditions we see around 

 us have been brought about. The progress of change in species, under 

 a state of nature, in relation to our idea of time, having been, on Mr. 

 Darwin's theory, so infinitely slow, he says we must not expect it to 

 be appreciable by our observation ; it rests, therefore, rather on 

 implied than historical evidence. In Chapter I. he fills up the gap 

 with a catalogue of facts bearing on the actual progress of variation 

 observed under domestication. Here we have not only the result, 

 but, knowing in most cases the condition of the originals of our 

 domestic productions, their state under domestication gives us a posi- 

 tive evidence of a certain amount of change. A kind of artificially- 

 produced plasticity of character, of both animals and plants that have 

 been domesticated, must be admitted ; but whether this, which is cer- 

 tainly proportionate to the artificial circumstances, has any relation 

 to " variation under nature," seems scarcely implied. Mr. Darwin 

 tells us that seedlings from the same fruit, and young of the same 

 litter, sometimes differ considerably from each other, though the 

 young and the parents have apparently been exposed to the same 

 conditions of life ; that the change of habit, under domestication, may 

 influence the relative proportions of the body, e.ff., "I find in the 

 domestic duck that the bones of the wing weigh less, and the bones 

 of the leg more, in proportion to the whole skeleton, than do the bones 

 of the wild duck ; and I presume that this change may be safely 

 attributed to the domestic duck walking more and flying less than its 

 wild parent ;" that the artificially-produced variation of one part of 

 an animal is frequently accompanied by a change in another part not 

 directly influenced, on a principle Mr. Darwin calls correlation of 

 growth, or relation in the characters of isolated members, e. g., 

 " breeders believe that long limbs are almost always accompanied by 

 an elongated head ; pigeons with short beaks have small feet, and 

 those with long beaks long feet ; hairless dogs have imperfect teeth ; 

 long-haired and coarse-haired animals, long or many horns," implying 

 that the impress of circumstances upon a particular function may also 

 involve the modification of other parts of the individual. The extent 

 of the fact of variation under domestication receives a strong illustra- 

 tion in the widely-different breeds of most of our domestic animals 

 and plants, which are supposed to have descended from single wild 

 stocks ; and Mr. Darwin says that it illustrates a similar principle he 



