280 THE WOKLD OF LIFE 



might become so rapidly improved that the danger from the 

 new environment would be overcome, and a new type might 

 be produced which would continue to be a dominant one un- 

 der the new conditions.^ 



N^ow, while it must be admitted, that under certain con- 

 ditions, and with certain classes of adaptations, the normal 

 effects of natural selection would be facilitated by the aid of 

 individual adaptation through use of organs, yet its effect is 

 greatly limited by the fact that it will not apply to several 

 classes of adaptations which are quite unaffected by use or 

 exercise. Such are the colours of innumerable species, which 

 are in the highest degree adaptive, either as protecting them 

 from enemies, as a warning of hidden danger (stings, etc.), 

 as recognition-marks for young or for wanderers, or by mimi- 

 cry of protected groups. Here the tise is simply being seen 

 or not seen, neither of which can affect the colour of the 

 object. Again, nothing is more vitally important to many 

 animals than the form, size, and structure of the teeth, which 



1 As many readers are ignorant of the extreme adaptability of many parts 

 of the body, not only during an individual life, but in a much shorter period, 

 I will here give an illustrative fact. A friend of mine was the resident 

 physician of a large county lunatic asylum. During his rounds one morning, 

 attended by one of his assistants and a warder, he stopped to converse with 

 a male patient who was only insane on one point and whose conversation 

 was very interesting. Suddenly the man sprang up and struck a violent 

 blow at the doctor's neck with a large sharpened nail, and almost com- 

 pletely severed the carotid artery. The warder seized the man, the assistant 

 gave the alarm, while my friend sat down and pressed his finger on the 

 proper spot to stop the violent flow of blood, which would otherwise have 

 quickly produced coma and death. Other doctors soon applied proper pres- 

 sure, and a competent surgeon was sent for, who, however, did not arrive 

 for more than an hour. The artery was then tied up and the patient got 

 to bed. He told me of this himself about two years afterwards, and, on 

 my inquiry how the functions of the great artery had been renewed, he 

 assured me that nothing but its permanent stoppage was possible, that 

 numerous small anastomosing branches enlarged under the pressure and 

 after a few months carried the whole current of blood that had before been 

 carried by the great artery, without any pain, and that at the time of speak- 

 ing he was quite as well as before the accident. Such a fact as this really 

 answers almost the whole of Herbert Spencer's argument which I have 

 quoted at p. 270. 



