CRUSTACEA AND MOLLUSCS 24! 



early crabs that had eyes already projecting on small 

 stalks, we should acknowledge that these had an 

 advantage, as they would perceive their enemies or 

 their food quicker than the others. In a word, the 

 changes that any organ or character of an animal shows 

 at birth must generally be so slight that they can have 

 no selective value ; that is to say, their owners cannot 

 be so much better situated on account of them as to 

 escape the destruction that falls on their fellows. 



Above all, it is said, we cannot see how complex 

 organs and instincts can have a selective value from the 

 beginning. The trunk is indispensable to the elephant. 

 It uses it as a weapon, conveys food to its mouth with 

 it, and cannot lift objects from the ground, or drink, 

 without it ; these are all actions that it could not perform 

 without the trunk on account of its short and stiff neck. 

 But the trunk is only useful at its actual length. If the 

 ancestors of the elephant had noses of ordinary length, 

 like the tapirs, they would hardly be able to perform one 

 of the above functions, and they would not have any 

 advantage in variations that added a small fraction of an 

 inch to them. We cannot admit, therefore, that the 

 first slight lengthening of the nose was so useful that 

 the elephants which did not possess it were the first to 

 perish. In other words, we do not see that these nasal 

 variations would have any selective value. 



However, let us take an instance from amongst our 

 own animals. Take the shell of the snails. This is 

 certainly useful to the animals, as they can withdraw 

 into it and find shelter from their enemies and from bad 



weather. But the shell did not appear at its full size all 



Q 



