CHAPTER X 

 SOME SPECIFIC CHARACTERS 



AN interesting case, showing that qualities which 

 are life-preserving under certain severe conditions 

 exist in some varieties of a species and not in 

 others, was recorded some eight years ago. After a very 

 severe "blizzard" 136 common sparrows were found be- 

 numbed on the ground by Professor Bum pus at Providence, 

 United States. They were brought into a warm room 

 and laid on the floor. After a short time seventy-two 

 revived and sixty-four perished. They were compared to 

 see if the survivors were distinguished by any measurable 

 character from those which died. It was found that the 

 survivors were smaller birds (the sexes and young birds 

 being separately compared) than those which died, and 

 were lighter in weight by one-twenty-fifth than the latter. 

 Also, the birds which survived had a decidedly longer 

 breastbone than those which died. 



Similarly, the late Professor Weldon found that in the 

 young of the common shore-crab, taken in certain parts 

 of Plymouth harbour, those with a little peculiarity in the 

 shape of the front of the shell survived when those without 

 this peculiarity died. Many thousands were collected 

 and measured in this experiment. It is not necessary 

 to suppose that the distinguishing mark of the survivors 

 in such cases is " the cause " of their survival. Such marks 

 as the breadth of the front part of the crab's shell and the 

 length of a bird's breastbone very probably are but " the 



