Natural Selection of Species. 107 



fatal to them. This proves that these species have received modifica- 

 tions which adapt them to the climate of their habitat. Every species 

 is known to do better in its own climate, and if transferred will either 

 die or become changed. The first apple trees introduced from the east 

 into Illinois refused to bear, and the results after years of experiment 

 were so discouraging that Horace Greeley, in an oration at an agricul- 

 tural fair, advised the Illinois farmers to abandon the attempt to raise 

 apples and attend exclusively to their reliable cereals. This advice 

 being disregarded, as is usual in such cases, Illinois now produces ap- 

 ples equal to any in the country and in abundance. But they are all of 

 different varieties from the stocks introduced from the east. The same 

 thing is happening in Minnesota. A number of excellent varieties have 

 been obtained totally different from anything to be found elsewhere and 

 yet related to those of other localities. In like manner the corn of Vir- 

 ginia or Tennessee will not ripen in Canada, but can by degrees be mod- 

 ified into a variety of corn that will. The Nasturtium is said to be 

 originally a native of Peru, where it is perennial. But introduced into 

 the United States, different varieties grow wild as annual or biennial and 

 rarely as perennial herbs. 



In the case of animal modifications the influences of climate are 

 equally potent, but are frequently or generally exercised indirectly by 

 modifying the habit of the animal. Thus it is said bees taken from the 

 United States to the Sandwich islands, after one or two seasons, finding 

 they could work the year round, ceased to store up honey in the hive. 



The woolly Elephants of Siberia were undoubtedly related to the 

 naked ones of Southern Asia, which was a case of simple climatic modi- 

 fication. But the modification of limbs and sense organs must gener- 

 ally be due to active habit, which is in turn determined by the circum- 

 stances of the environment including climate. 



Darwin gives many examples. The- fish and other animals in caves 

 are often blind from disuse of their eyes. < ' In some of the crabs the 

 foot stalk for the eye remains though the eye is gone. " " The eyes of 

 moles and some burrowing rodents are rudimentary in size and in some 

 cases quite covered up by skin and fur," due no doubt to gradual dis- 

 use. There are several kinds of birds that cannot fly, as Ostriches, Cas- 

 sowaries, the Loggerheaded Duck of South America and the Apteryx. 

 This last is modified from the ordinary bird type, also, in having a com- 

 plete diaphragm, in not having abdominal air cells, and in the circum- 

 stance of its bones not being hollow. These modifications obviously go 

 along with the discontinuance of flight, since the lightness of bone and 

 extra aeration of the blood are no longer required. 



The effects of disuse in reducing useful organs to rudiments has al- 

 ready been incidentally mentioned in speaking of those rudiments which 



