456 



SCIENCE 



[N. S. Vol. XXXVIII. No. ! 



Boulenger without hesitation has deter- 

 mined as TypJilops braminus. Now, whilst 

 this genus of wormlike, blind little snakes 

 has a wide circumtropical distribution, T. 

 hraminus had hitherto been known only 

 from the islands and countries of the In- 

 dian Ocean basin, never from America, nor 

 from any of the Pacific Islands which pos- 

 sess other kinds of Typhlops. Accidental 

 introduction is out of the question. Al- 

 though the genus is, to judge from its 

 characters, an especially old one, we can 

 not possibly assume that the species bram- 

 inus, if the little thing had made its way 

 from Asia to Mexico by a natural mode of 

 spreading, has remained unaltered even to 

 the slightest detail since that geological 

 epoch during which such a journey could 

 have taken place. There remains the as- 

 sumption that amongst the of course count- 

 less generations of Typhlops in Mexico 

 some have hit off exactly the same kind of 

 permutation and combination of those 

 characters which we have hitherto consid- 

 ered as specific of braminus, just as a pack 

 of cards may in a long series of deals be 

 dealt out more than once in the same 

 sequence. 



The two cases are impressive. They re- 

 minded me vividly that many examples 

 of very discontinuous distribution — which 

 any one 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 com- 

 parative anatomy by basing it upon the 

 theory of descent. The leading idea in all 

 his great works is to show that transforma- 

 tion, "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 this new line is his class- 

 ical treatise on the carpus and tarsus 

 (1864). 



It followed from this point of view that 

 the degree of resemblance in structure be- 

 tween homologous organs and the number 

 of such kindred organs present is a meas- 

 ure for the affinity of their owners. So 

 was ushered in the era of pedigrees of 

 organs, of functions, of the animals them- 

 selves. The tracing of the divergence of 

 homogenous parts became all-important, 

 whilst those organs or features which re- 

 vealed themselves as of different origin, 

 and therefore as analogous only, were dis- 

 carded as misleading in the all-important 

 search for pedigrees. Functional corre- 

 spondence was dismissed as "mere anal- 

 ogy, ' ' and even the systematist has learned 

 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 abol- 

 ished both sets of characters, the so-called 

 fundamental or "reliable" as well as the 

 analogous. 



As A. Willey 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 



