184 



SCIENCE. 



[N. S. Vol.. IV. No. 85. 



one of the great objects of morphology to 

 construct, and thus to correct the results 

 obtained by the other methods of inquiry. 



Paleontology further enables us accurately 

 to discriminate between resemblances which 

 are due to genetic af&nity and those which 

 result from parallelism or convergence. 



To illustrate : On grounds of comparative 

 anatomy, Flower classified the land Car- 

 nivora in three sections : the Cynoidea, or 

 dogs ; the Arctoidea, containing the bears, 

 raccoons and mustelines ; and the Aeluro- 

 idea, including the civets, hyenas and cats. 

 This classification has found wide favor and 

 very general acceptance, but paleontology 

 proves it to be untenable. The extinct 

 phyla show that the dogs and bears are 

 very closely akin, as are .the mustelines, 

 civets and hyenas, while the cats occupy a 

 very isolated position and are not nearly 

 allied to any of the other families. The 

 anatomical characters which suggested 

 Flower's system are, in part, examples of 

 convergence, and in part, due to the reten- 

 tion of primitive characters in some groups 

 and their loss in others. 



Again, reasoning from embrj^ological 

 data, Eose and others have propounded the 

 theory that the complex, multicuspidate, 

 mammalian tooth has been formed by the 

 coalescence of many simple teeth. The 

 phyletic series enable us to follow the evo- 

 lution of these teeth step by step, and de- 

 monstrate the incorrectness of the ' con- 

 crescence theory.' In fact, the great lesson 

 which the study of the phyla continually 

 brings home to the observer is that trust- 

 worthy results are to be obtained only by 

 the laborious and minute tracing of the 

 changes through every step of the way. 

 Fragmentary series are not to be depended 

 upon, and the wider the gaps between their 

 members the more uncertain is their con- 

 nection. 



(2) The reconstruction of pedigrees, the 

 solving of homologies, the determination of 



relationships, and the establishing of classi- 

 fication upon a sound and natural basis^ 

 important as these are, are yet only a part 

 of the great task which morphology has set 

 before itself. AVe wish to penetrate more 

 deeply into the mystery of nature and learn 

 how and why these changes have occured • 

 or, in other words, to discover the manner 

 in which, and the efficient causes by which^ 

 development is effected. On these subjects 

 there is, as yet, wide divergence of view 

 among morphologists. The postulates and 

 assumptions upon which morphological dis- 

 cussions are founded are, in great measure, 

 incapable of proof, and appeal with very 

 different degrees of force to diff"erent minds. 

 Modes of development which appear axio- 

 matic to one observer are by another re- 

 garded as absurd. All are agreed that 

 there are limits to the possibilities of 

 change ; no one attempts to derive a butter- 

 fly from a beetle, or a horse from a cow; 

 but just how and where these limits should 

 be drawn it is at present impossible to say. 

 It is this uncertainty which refers the 

 question to the individual judgment and 

 leaves the way open for such radical differ- 

 ences of opinion. 



To the solution of these problems of evo- 

 lutionary modes paleontology offers most 

 valuable assistance, drawn from the study 

 of actual phyla. It might seem that this 

 was merely arguing in a circle, because the 

 construction of phylogenetic series involves 

 certain presuppositions as to what changes 

 are and what are not possible, and we then 

 proceed to prove the presuppositions by the 

 phyla thus constructed. But the cautious, 

 step-by-step method, guarded by the order 

 of appearance in time, offers a way of escape, 

 and enables us to construct phyla in har- 

 monious structural and stratigraphical suc- 

 cession, which must very neai'ly represent 

 the actual stages of change. Only a be- 

 ginning has been made in this work, but the 

 results drawn from an examination of 



