236 MORPHOLOGY. [Chap. XIV. 



consequently always have fewer legs; or conYersely, those 

 with many legs have simpler mouths? Why should 

 the sepals, petals, stamens, and pistils, in each flower, 

 though fitted for such distinct purposes, be all con- 

 structed on the same pattern? 



On the theory of natural selection, we can, to a cer- 

 tain extent, answer these questions. We need not here 

 consider how the bodies of some animals first became 

 divided into a series of segments, or how they became 

 divided into right and left sides, with corresponding 

 organs, for such questions are almost beyond investiga- 

 tion. It is, however, probable that some serial struc- 

 tures are the result of cells multiplying by division, 

 entailing the multiplication of the parts developed from 

 such cells. It must sufl&ce for our purpose to bear in 

 mind that an indefinite repetition of the same part or 

 organ is the common characteristic, as Owen has re- 

 marked, of all low or little specialised forms; therefore 

 the unknown progenitor of the Vertebrata probably pos- 

 sessed many vertebrae; the unknown progenitor of the 

 Articulata, many segments; and the unknown progeni- 

 tor of flowering plants, many leaves arranged in one 

 or more spires. We have also formerly seen that parts 

 many times repeated are eminently liable to vary, not 

 only in number, but in form. Consequently such parts, 

 being already present in considerable numbers, and 

 being highly variable, would naturally afford the ma- 

 terials for adaptation to the most different purposes; 

 yet they would generally retain, through the force of 

 inheritance, plain traces of their original or fundamental 

 resemblance. They would retain this resemblance all 

 the more, as the variations, which afforded the basis for 

 their subsequent modification through natural selection. 



