

408 



CONCLUDING REMARKS. 



Chap. XXVIII. 



they often ig 



the whole subject of geographical distribu 



tion as completely as if its laws were the result of chance 



Although from the reasons just assigned it is often difficult 

 to judge accurately of the amount of change which our domesti- 

 cated productions have undergone, yet this can be ascertained 

 in the cases in which we know that all the breeds are descended 

 from a single species, as with the pigeon, duck, rabbit, and almost 



certain 



ly with the fowl ; and by the aid of analogy 



al wild 



possible in the 



of animals descended fr 



m 



the 



stocks. It is impossible to read the details g. 

 lier chapters, and in many published works, o 



- 



visit our various exhibitions, without being deeply impressed 

 with the extreme variability of our domesticated animals and 

 cultivated plants. I have in many instances purposely given 

 details on new and strange peculiarities which have arisen. 



part of the 



escapes the tendency 



generally affect parts of small vital or phy 



y 



No 



The 



impor 



but so it is with the differ 



which exist 



between closely allied species. In these unimportant cha- 

 racters there is often a greater difference between the breeds of 

 the same species than between the natural species of the same 

 genus, as Isidore Geoffroy has shown to be the case with size, 

 and as is often the case with the colour, texture, form, &c, of 

 the hair, feathers, horns, and other dermal appendages. 



It has often been 



ted that important parts never vary 



under domestication, but this is 



plete error. Lool 



the skull of the pig in any one of the highly improved breeds 



with the occipital condyles and other parts greatly modified 



look 



of the 



of the rabbit, observe the 



Or again, in the several breeds 



shaped 



gated 



the differently 



pital foramen, atlas, and other cervical vertebr 



The whole shape of the brain, together with the skull, has 

 been modified in Polish fowls; in other breeds of the fowl 

 the number of the ve 



tebrae and the for 



of the 



vertebrae have been changed. In certain pigeons the shape of 

 the lower jaw, the relative length of the tongue, the size of the 

 nostrils and eyelids, the number and shape of the ribs, the form 

 and size of the oesophagus, have all varied. In certain quadru- 

 peds the length of the intestines has been much increased or 



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