104 CONCLUDING EEMAEKS. Chap. XXYIIL 



skull, has been modified in Polish fowls : in other breeds of 

 the fowl the number of the vertebrae and the forms of the 

 cervical vertebrae have been changed. In certain pigeons the 

 shape of the lover 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 quadrupeds the length of the intestines has been much 

 increased or diminished. With plants we see wonderful 

 differences in the stones of various fruits. In the Cucur- 

 bitaceee several highly important characters have varied, such 

 as the sessile position of the stigmas on the ovarium, the 

 position of the carpels, and the projection of the ovarium out 

 of the receptacle. But it would be useless to run through 

 the many facts given in the earlier chapters. 



It is notorious how greatly the mental disposition, tastes, 

 habits, consensual movements, loquacity or silence, and tone 

 of voice have varied and been inherited in our domesticated 

 animals. The dog offers the most striking instance of changed 

 mental attributes, and these differences cannot be accounted 

 for by descent from distinct wild types. 



Xew characters may appear and old ones disappear at any 

 stage of development, being inherited at a corresponding 

 stage. Y\ e see this in the difference between the eggs, the 

 down on the chickens and the first plumage of the various 

 breeds of the fowl; and still more plainly in the differences 

 between the caterpillars and cocoons of the various breeds of 

 the silk-moth. These facts, simple as they appear, throw light 

 on the differences between the larval and adult states of 

 allied natural species, and on the whole great subject of em- 

 bryology. Xew characters first appearing late in life are apt 

 to become attached exclusively to that sex in which they 

 first arose, or they may be developed in a much higher degree- 

 in this than in the other sex ; or again, after having become 

 attached to one sex, they may be transferred to the opposite 

 sex. These facts, and more especially the circumstance that 

 new characters seem to be particularly liable, from some 

 unknown cause, to become attached to the male sex, have an ' 

 important bearing on the acquirement of secondary sexual 

 characters by animals in a state of nature. 



