Casting Off the Useless Organs 



bones, joints and fingers of the fore feet that were used 

 when their forefathers roamed in herds upon the land; and 

 buried still deeper beneath the surface of the breast, the 

 rudiments of the ancestral hind feet may still be found. The 

 life history of the seals, walrus, sea cows, dolphins and all 

 the other sea mammals may be traced in a similar manner. 

 The vestigial organs in all of these tell the evolutionary 

 story of their lives. In like manner the rudiments of out- 

 grown organs may be found in practically all the bodies of 

 all land animals which is the most persuasive and convincing 

 proof that these changes have been brought about by adapta- 

 tions to meet the conditions of changing environments. 



The snail furnishes an example of the power of the Mol- 

 lusca to cast off useless organs and to adapt their lives to 

 changed environment. Its ancestors made their homes in 

 the sea and there built houses around their bodies in the 

 form of shells as a protection against their enemies. Either 

 voluntarily or involuntarily, its ancient ancestors were cast 

 upon or crawled out upon the seashore and were cut off by 

 some obstruction and forced to adapt themselves to land 

 conditions. While its ancestors remained in the sea, it was 

 apparently an easy matter to construct its house, beautiful 

 in design and coloring, from the minerals carried in solu- 

 tion in the waters surrounding it. But when its environment 

 had changed and the materials from which its shell was made 

 were removed, it had to set about making its shell in another 

 way or live without one. Limestone is simply a collection 

 of minute sea shells that have formed in the waters of the 

 early sea. The snails seized upon this substance and began 

 to construct their homes from the fossil remains of their 



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