16 Hans Gadow. 



influences. they are sifting- themselves into iiew varieties in kaleido- 

 scopic fashion. By accident of Isolation in particularly favoured 

 localities an identical Variation may become dominant for a time, 

 as a local race, being-, in such a case instances of „discontinuous 

 distribution", in reality due to „parallel evolution". Parallel, not 

 convergent, since they have reached the identical condition througli 

 corresponding stages. Shifting of the habitat, an unavoidable result 

 of their spreading (and they must spread if they multiply) will put 

 an end to their epistasis, or apparent perraanence of that local race. 



Orthogenesis is not necessarily a good thing; its momentum, to 

 a great extent due to cumulative inheritance, often leads to deplo- 

 rable results, and it remains to be shown whether monochrome red 

 snakes are better off than their more oldfashioned banded relations, 



It is raost likely that Natural Selection considers these varia- 

 tions as going too far, and calls a halt, but this is not what is 

 meant by Epistasis. By ruthlessly cutting down every tree before 

 it has reached its attainable height w^e cannot prevent the rest 

 from growing. Mehely's Statement that Epistasis is caused by the 

 „Ungunst der Verhältnisse" is therefore not happily conceived, and 

 is liable to be misunderstood. Unless it is merely a commonplace, 

 it can mean only — to take a concrete example, that the fixing of 

 a tricoloured race with lopsided pattern, is an unfortunate Inhibition. 

 For all we know to the contrary such a dress may be more advantageous 

 in certain localities than the more advanced stage Avith regularly 

 arranged rings, provided always that these variations do matter at 

 all. The Stag with eight points has a more dangerous weapon than 

 the one with sixteen and if the latter goes back to ten (owing to 

 unfavourable conditions, as food, age etc.) it conceivably retrieves its 

 apparent loss. 



A List of Snakes with Elapoid coloration. 



I. El (t 2)1 II (IC '^ proteroglyphous and very poisonous. 



Elaps, most of the two dozen or more species, for instance: 



E. fulvkis, from Venezuela to South Eastern U. S. A. 



E. euryxanthus, Arizona and Sonora. 



E. corullinus, Tropica! South America and Lesser Antilles. 



E. marcgravi, Tropical South America. 



E. stirinaiiieM.sis, Tropical South America. 



E. clegans, Guatemala to Vera Cruz. 



Callophis viacclellandi and C. hibroni, Assam to Southern China. 



