To demonstrate that the chanL2;es mentioned above 

 have not ceased altogether, and to show that, at present 

 times, changes of a very marked character are still be- 

 ing effected, it is necessary only to point out the fact 

 that the level of Lake Erie is continually falling. The 

 old shore lines, which indicate the former limits of the 

 lake, are to be seen for many miles from the present 

 water margins. Prese]ue Isle, a; peninsula extending 

 into the lake at Erie, has been moving eastward for 

 over six hundred years and it is still in a state of con- 

 tinuous motion and change. 



On this peninsula old ponds are disappearing 

 while new ponds are being formed. The w^hole con- 

 tour of the peninsula, which is now a state park, is so 

 rapidly changing that these changes may be noted from 

 year to year. 



Both the Atlantic and Pacific coasts are likewise 

 showing a constant variation. Shore lines are advanc- 

 ing at certain points and receding at others. Thus, we 

 see that the old hymn, "Change and Decay In All 

 Around I See," is an expression of reality. 



The Science of Ecology, or the study of organism 

 and their relation to the environment, has shown that 

 there is a definite relationship between an animal and 

 the conditions under which it lives. In fact, it is the 

 environment which largely determines the animal asso- 

 ciation to be found in a given place. The significance 

 of this is emphasized by observing specialized adapta- 

 tions to water; to burrowing in the ground; to arboreal 

 existence, etc. If any one of these conditions were to 

 be suddenly removed, the animals mostly highly spec- 

 ialized to it would perish. If conditions were to change 

 gradually the weaker ones would probably perish, but 



-..H[ 21 >«- 



