首页其他书籍The Conditions of Existence[mobi] [azw3] [epub] [txt] [pdf] 

The Conditions of Existence

其他书籍

作者:Huxley、ThomasHenry等        

出版时间:2019-09-18        格式:[mobi] [azw3] [epub] [txt] [pdf]         

豆瓣评分
用心爱 书童

    本书由 用心爱 共享发布,请大家多多支持!

  • 详细介绍
  • 热门书评

精彩书摘

  Breeds,known to have been derived from a common stock by selection,may be as different in their structure from the original stock as species may be distinct from each other.
  But is the like true of the physiological characteristics of animals?
  Do the physiological differences of varieties amount in degree to thoseobserved between forms which naturalists call distinct species?This is a most important point for us to consider.
  As regards the great majority of physiological characteristics,there is no doubt that they are capable of being developed,increased,and modified by selection.
  There is no doubt that breeds may be made as different as species in many physiological characters.I have already pointed out to you very briefly the different habits of the breeds of Pigeons,all of which depend upon their physiological peculiarities,——as the peculiar habitof tumbling,in the Tumbler——the peculiarities of flight,in the "homing"birds,——the strange habit of spreading out the tail,and walking in a peculiar fashion,in the Fantail,——and,lastly,the habit of blowing out the gullet,so characteristic of the Pouter.These are all due to physiological modifications,and in all these respects these birds differ as much from each other as any two ordinary species do.

热门书评共 0 条评论

    未登录,还无法评论,请先

资源
共享
作品反馈
  • 请详述反馈内容,侵权删除需提交后补填相关授权文件!