CuAP. XIII. MORPHOLOGY. 39I 



ogous. The wliole subject is included under the general term 

 of Morphology. This is the most interesting department of 

 natural history, and )nay be said to be its very soul. What 

 ean bo more curious than that the hand of a man, formed for 

 grasping, that of a mole for digging, the leg of the horse, the 

 paddle of the porpoise, and the wing of the Ijat, should all be 

 constructed on the same pattern, and should include similar 

 bones, ia the same relative positions ? Geoflroy St.-Hilaire 

 has insisted strongly on the high importance of relative posi- 

 tion or connection in homologous parts ; they naay diifer to 

 almost any extent in form and size, and yet will remain con- 

 nected together in the same invariable order. We never find, 

 lor instance, the bones of the arm and forearm, or of the thigh 

 and leg, trans^wsed. Hence the same names can be given to 

 tJie homologous lx)ncs in widely-dillercnt animals. Wc see 

 the sanje great law in the construction of the mouths of in- 

 sects ; what can be more diflerent than the immensely long 

 spiral pn>])oscis of a sphinx-moth, the curious folded one of a 

 hcc or bug, and the great jaws of a beetle ? — yet all these or- 

 gans, serving for such Avidely-diflerent purjwses, are formed by 

 infinitely-numerous modifications of an upper lij"), mandibles, 

 and two pal is of maxilkc. The same law governs the con- 

 struction of the mouths and limbs of crustaceans. So it is 

 with the flowers of plants. 



Nothing can be more hopeless than to attempt to explain 

 this similarity of pattern in members of the same class, by util- 

 ity or by the doctrine of final causes. The hoi^elessness of the 

 attempt has been expressly admitted by Owen in his most 

 interesting work on the " Nature of Limbs." On the ordinary 

 \iew f)f the independent creation of each being, we can only 

 say that so it is — that it has pleased the Creator to construct 

 all the animals and plants in each p^eat class on a uniform 

 j)lan : but this is not a scientific explanation. 



The exjilanatitjn is manifest according to the theory of the 

 si'lection of successive slight modifications — each modification 

 Ijeing profitable in some way to the modified form, but often 

 alVecting by correlation other parts of the organization. In 

 clianges of this nature, there Avill be little or no tendency to 

 alter tlie origiiud pattern, or to trans[)ose the parts. The 

 l)ones of a limb might be shortened and ilattencil to any ex- 

 tent, becoming at the same time enveloj)ed in tliick membrane, 

 so as to serve as a fin ; or a webbed liand might have all its 

 bones, or certain bones, lengthened to any extent, with the 



