MORPHOLOGY ♦?$ 



are nomoiogous — that is, correspond in number and in rela- 

 tive connexion — with the elemental parts of a certain number 

 of vertebrae. The anterior and posterior limbs in all the 

 higher vertebrate classes are plainly homologous. So it is 

 with the wonderfully complex jaws and legs of crustaceans. 

 It is familiar to almost every one, that in a flower the rela- 

 tive position of the sepals, petals, stamens, and pistils, as well 

 as their intimate structure, are intelligible on the view that 

 they consist of metamorphosed leaves, arranged in a spire. 

 In monstrous plants, we often get direct evidence of the pos- 

 sibility 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 

 other animals, that organs, which when mature become ex- 

 tremely 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 en- 

 closed in a box composed of such numerous and such extra- 

 ordinarily shaped pieces of bone, apparently representing ver- 

 tebrae? As Owen has remarked, the benefit derived from the 

 yielding of the separate pieces in the act of parturition 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 different purposes, namely 

 flying and walking? Why should one crustacean, which has 

 an extremely complex mouth formed of many parts, conse- 

 quently 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 purposes, 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 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 investigation. It is, however, probable 

 that some serial structures are the result of cells multiply- 

 ing by division, entailing the multiplication of the parts 



