COMPARATIVE ANATOMY AND MORPHOLOGY 345 



homologies, in opposition to those which we have examined above 

 and which are the special homologies. 



Thus we have been asked if the occipital bone is homologous to the 

 vertebrae, the humerus to the femur, the hand to the foot, etc. 



For the partisans of the theories of unity of plan, of prototype, or 

 of archetype, the problem of the general homologies does not differ 

 essentially from that of the special homologies. Unity of plan may 

 manifest itself as well in the parts of the same creature as in different 

 creatures. The prototype or the archetype may be conceived as having 

 the hand identical with the foot and the occipital formed like a 

 vertebra. For the partisans of modern ideas, the matter is a little 

 more difficult, for there is no ancestral type in which respectively the 

 hand and foot, the leg and the arm, the occipital and the vertebrae, 

 are represented by single structures, so that the problem for the trans- 

 formists appears quite as subjective a one as for the philosophers 

 who preceded them. The transformists have succeeded, moreover, in 

 giving to the solution of the problem a certain objectivity, reasoning 

 in the following manner: if the occipital were formed exactly like 

 a vertebra, the foot like the hand, the femur like the humerus, we 

 should not hesitate to consider them as homologous, just as we do 

 not contest the homology of the vertebrae among themselves. If, 

 then, in descending the scale of beings by means of comparative 

 anatomy, if in constructing phylogeny by means of paleontology and 

 embryology, we find beings or stages where those parts which we 

 are comparing are more and more similar among themselves, even 

 to the point of being identical, we should have the right to homologize 

 them; otherwise, not. Thus we have come to recognize that the occi- 

 pital is not a vertebra, and that the homologue of the tibia is, in the 

 forearm, the radius, although in a superficial examination it would 

 appear to be the ulna, as some anatomists, experts in their science, 

 too, have drawn and described it. 



Since we have now shown what comparative anatomy is according 

 to generally admitted ideas and under its three aspects, namely : the 

 presentation of zootomical ideas in an arrangement facilitating the 

 comparison of organs, the search for the law r s of organization, and the 

 search for homologies, we must now go more deeply into our subject 

 and examine the bearing of comparative anatom^, the value of its 

 results, and the solidity of its conceptions. 



As far as the first two aspects of comparative anatomy are con- 

 cerned, we have little to add to what we have already said. 



We must recognize that in so far as comparative anatomy limits 

 itself to presenting zootomical facts in another order, it is not a true, 

 independent science, neither in its foundations nor in its results; it 

 is nevertheless extremely useful, indispensable even in furnishing not 

 only to the student, but also to the scholar, a larger view of things, 



