66 THE THEORY OF EVOLUTION 



Species' one of the great stumbling blocks in the 

 way of the theory of special creation was the existence 

 in a great many animals of rudimentary organs, or 

 such as are so far reduced and atrophied as to be of 

 no service to their possessors. An analogy employed 

 by my lamented friend, Mr. Richard Lydekker, may 

 be advantageously repeated here. Let us suppose 

 that a screw-steamer, with longitudinal shaft lead- 

 ing aft from the engine-room to the stern, where it 

 carries the propeller, should, on close examination, 

 reveal many signs that it had originally been a "side 

 wheeler," or paddle-boat. Recognizable remnants of 

 paddle-boxes, of bearings for a transverse shaft, and 

 the like, are found; what would be the inevitable 

 conclusion? No one would maintain that a naval 

 architect, in possession of his senses, in constructing a 

 screw-steamer would deliberately introduce features 

 which are useful and appropriate only in a paddle- 

 boat. The only reasonable explanation would be 

 that the vessel had originally been built as a paddle- 

 boat and had subsequently been converted into a 

 screw-steamer and in the conversion it had not been 

 found necessary completely to eradicate all traces of 

 the original construction. Obviously, the same rea- 

 soning applies to rudimentary organs. The only 

 satisfactory explanation of such useless remnants is 

 that their possessors are descendants of ancestors in 

 which those organs were fully functional. It seems 

 quite absurd to assume that, in a separately and 

 specially created animal, useless structures, reminis- 



