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BEITISH ASSOCIATION FOE THE ADVANCEMENT OF 

 SCIENCE, BIEMINGHAM, 1913. 



ADDEESS TO THE ZOOLOGICAL SECTION. 



By H. F. Gadow, M.A., Ph.D., F.R.S., President of the Section. 



" Addeess your audience about what you yourself happen to be 

 most interested in, speak from the fullness of your heart, and make a 

 clean breast of your troubles." That seemed good advice, and I shall 

 endeavour to follow it, taking for my text old and new aims and 

 methods of morphology, with special reference to resemblances in 

 function and structure on the part of organs and their owners in the 

 animal kingdom. First, however, allow me to tell you what has 

 brought me to such a well-worn theme. Amongst the many im- 

 pressions which it has been my good luck to gather during my travels 

 in that enchanting country Mexico are the two following : — 



First, the poisonous Coral snakes, Elaps, in their beautiful black, 

 red, and yellow garb ; it varies in detail in the various species 

 of Elaps, and this garb, with most of the variations too, occurs also 

 in an astonishing number of genera and families of semi-poisonous 

 and quite harmless Mexican snakes, some of which inhabit the same 

 districts. A somewhat exhaustive study of these beauties has shown 

 incontestably that these often astoundingly close resemblances are 

 not cases of mimicry, but due to some other co-operations. 



Secondly, in the wilds of the State of Michoacan, at two places, 

 about twenty and seventy miles from the Pacific Coast, I myself col- 

 lected specimens of Typhlops which Dr. Boulenger without hesitation 

 has determined as Typhlops braminus. Now, whilst this genus of 

 wormlike, blind little snakes has a wide circumtropical distribution, 

 T. braminus had hitherto been known only from the islands and 

 countries of the Indian Ocean basin, never from America, nor from 

 any of the Pacific Islands which possess other kinds of Typhlops. 

 Accidental introduction is out of the question. Although the genus 

 is, to judge from its characters, an especially old one, we cannot 

 possibly assume that the species braminus, 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 geolo- 

 gical epoch during which such a journey could have taken place. 

 There remains the assumption that amongst the of course countless 

 generations of Typhlops in Mexico some have hit off exactly the 

 same kind of permutation and combination of those characters which 

 we have hitherto considered 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 reminded me vividly that 

 many examples of very discontinuous distribution — which anyone 



