22 EVOLUTION. 



muscles ' so as to expose them ready for action, like 

 a dog prepared to fight." 



Wilson also notes instances of rudiments in the 

 plant kingdom. 



Resemblance, 



The similarity in the structure of animals of the 

 same great divisions, though of different species, is a 

 special proof of Evolution. The members of each 

 great class are identical in their general plan. For 

 instance, — the articulates, or jointed animals, have 

 the heart in the upper part of the body, the diges- 

 tive system in the middle, and the nervous system in 

 the lower part. Lobsters, crabs, barnacles, butter- 

 flies, spiders, and all the thousands of species of 

 insects agree in these particulars. In the vertebrates 

 the position is reversed ; the nervous system is on 

 top and the heart is at the bottom of the body. 

 There are always two pairs of limbSi represented in 

 the fish by fins, in the bird by legs and wings, in 

 beasts by four legs, and in man by legs and arms. 

 Fish, frog, reptile, quadruped, and man all possess 

 these peculiar features. The molluscs are dis- 

 tinguished by having the nervous system in three 

 great masses. Oysters, cockles, snails, whelks, and 

 cuttle-fishes all agree in this. The radiates have all 

 their parts arranged uniformly in lines diverging 

 from a centre, much like the parts of a flower. Sea- 

 urchins, starfishes, etc., are of this type. 



