J MORPHOLOGY. 426 



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 crusta- 

 ceans. It is familiar to almost every one, that in a flower 

 the relative 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 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 other 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 

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

 traordinarily shaped pieces of bone, apparently representing 

 vertebrae ? 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 construc- 

 tion 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, 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 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 

 developed from such cells. It must suffice 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 specialized forms ; therefore the 

 unknown progenitor of the Yertebrata probably possessed 



