MORPHOLOaT. 453 



leaves, arranged in a spire. In monstrous plants, we often 

 get direct evidence of the possibility of one organ being 

 transformed into another; and we can actually see, during 

 the early or embryonic stages of development in flowers, as 

 well as in crustaceans and many otlier animals, that organs 

 which when mature become extremely different are at first 

 exactly alike. 



How inexplicable are the cases of serial homologies on 

 the ordinary view of creation! Why should the brain be 

 inclosed in a box composed of such numerous and such ex- 

 traordinarily shaped pieces of bone, apparently represent- 

 ing vertebrse? As Owen has remarked, the benefit derived 

 from the yielding of the separate pieces in the act of par- 

 turition by mammals, will by no means explain the same 

 construction in the. skulls of birds and reptiles. Why 

 should similar bones have been created to form the wing 

 and the leg of a bat, used as they are for such totally differ- 

 ent purposes, namely, flying and walking? Why should 

 one crustacean, which has an extremely complex mouth 

 formed of many parts, consequently always have fewer 

 legs; or conversely, those with many legs have simpler 

 , mouths? Why should the sepals, petals, stamens and 

 pistils, in each flower, though fitted for such distinct pur- 

 poses, be all constructed on the same pattern? 



On the theory of natural selection, we can, to a certain 

 extent, answer these questions. We need not here con- 

 sider 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 investigation. It is, however, 

 probable that some serial structures are the result of cells 

 multiplying by division, entailing the multiplication of the 

 parts developed from such cells. It must suffice for our 

 purpose to bear in mind that an indefinite repetition of the 

 same partj)r organ is the common characteristic, as Owen 

 has remarked, of all.low or little specialized forms; there- 

 fore the unknown progenitor of the Vertebrata probably 

 possessed many vertebra; the unknown progenitor of the 

 Articulata, many segments; and the unknown progenitor 

 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. 



