: 



106 LAY SERMONS, ADDRESSES, AND REVIEWS. [vi 



propeller : seize it, and it will show you that its great 

 claws are no mean weapons of offence ; suspend a piece 

 of carrion among its haunts, and it will greedily devour 

 it, tearing and crushing the flesh by means of its multi- 

 tudinous jaws. 



Suppose that we had known nothing of the lobster 

 but as an inert mass, an organic crystal, if I may use the 

 phrase, and that we could suddenly see it exerting all 

 these powers, what wonderful new ideas and new ques- 

 tions would arise in our minds ! The great new question 

 would be, " How does all this take place ? " the chief new 

 idea would be, the idea of adaptation to purpose, — the 

 notion, that the constituents of animal bodies are not 

 mere unconnected parts, but organs working together to 

 an end. Let us consider the tail of the lobster aefain 

 from this point of view. Morphology has taught us 

 that it is a series of segments composed of homologous 

 parts, which undergo various modifications — beneath 

 and through which a common plan of formation is dis- 

 cernible. But if I look at the same part physiologically, 

 I see that it is a most beautifully constructed organ ol 

 locomotion, by means of which the animal can swiftly 

 propel itself either backwards or forwards. 



But how is this remarkable propulsive machine made 

 to perform its functions ? If I were suddenly to kill one 

 of these animals and to take out all the soft parts, I 

 should find the shell to be perfectly inert, to have no 

 more power of moving itself than is possessed by the 

 machinery of a mill, when disconnected from its steam- 

 engine or water-wheel. But if I were to open it, and 

 take out the viscera only, leaving the white flesh, I 

 should perceive that the lobster could bend and extend 

 its tail as well as before. If I were to cut off the tail, I 

 should ceaseto find any spontaneous motion in it ; but 

 on pinching any portion of the flesh, I should observe 



