356 THE ZOOLOGIST. 



who has worked at zoogeography will call to mind — are exhibited by 

 genera, families, and even orders, without our knowing whether the 

 groups in which we class them are natural or artificial. The ultimate 

 appeal lies with anatomy. 



Introduced to Zoology when Haeckel and Gegenbaur were both 

 at their zenith, I have been long enough a worker and teacher to feel 

 elated by its progress and depressed by its shortcomings and failures. 

 Perhaps we have gone too fast, carried along by methods which have 

 yielded so much, and therefore have made us expect too much from 

 them. 



Gegenbaur founded the modern comparative anatomy by basing 

 it upon the theory of descent. The leading idea in all his great 

 works is to show that Transformation, "continuous adjustment" 

 (Spencer), has taken place ; he stated the problem of comparative 

 anatomy as the reduction of the differences in the organization of the 

 various animals to a common condition ; and as homologous organs 

 he defined those which are of such a common, single, origin. His first 

 work in tbis new line is his classical treatise on the Carpus and Tarsus 

 (1864). 



It followed from this point of view that the degree of resemblance 

 in structure between homologous organs and the number of such 

 kindred organs present is a measure for tbe affinity of their owners. 

 So 'was usbered in the era of pedigrees of organs, of functions, of the 

 animals themselves. The tracing of the divergence of homogenous 

 parts became all- important, whilst those organs or features which 

 revealed themselves as of different origin, and therefore as analogous 

 only, were discarded as misleading in the all-important search for 

 pedigrees. Functional correspondence was dismissed as " mere 

 analogy," and even the systematist has learnt to scorn these so-called 

 physiological or adaptive characters as good enough only for artificial 

 keys. A curious view of things, just as if it was not one and the 

 same process which has produced and abolished both sets of 

 characters, the so-called fundamental or " reliable " as well as the 

 analogous. 



As A. YYilley has put it happily, there was more rejoicing over the 

 discovery of the homology of some unimportant little organ than over 

 the finding of the most appalling unrelated resemblance. Morphology 

 had become somewhat intolerant in the application of its canons, 

 especially since it was aided by the phenomenal growth of Embry- 

 ology. You must not compare ectodermal with endodermal products. 

 You must not make a likeness out of another germinal layer or any- 

 thing that appertains to it, because if you do that would be a horror, 

 a heresy, a homoplasy. 



Haeckel went so far as to distinguish between a true Homology, 

 or Homophyly, which depends upon the same origin, and a false 

 Homology, which applies to all those organic resemblances which 

 derive from an equivalent adaptation to similar developmental con- 

 ditions. And he stated that the whole art of the morphologist con- 

 sists in the successful distinction between these two categories. If 

 we were able to draw this distinction in every case, possibly some 



