HERPETOLOGY OF THE GRAND DUCHY OF BADEN. 339 



or yellow colour gradually assumes a dirtier tint, resembling a 

 thin coating of brown dust, and becomes less sharply defined in 

 proportion as the darker patches encroach upon it from all sides. 

 These in their turn melt imperceptibly into the brown or grey 

 colour of the head and back, and it is noticeable that the black 

 border itself is often less intensely coloured with adults than with 

 the young. Sometimes one side of the collar remains almost 

 white, while the other has already nearly faded away. 



To judge by a considerable selection of heads showing these 

 transitional stages, I gather that the process is in all cases 

 identical. In some Italian specimens all traces of the collar 

 have vanished ; with others, from Baden, they are still to be 

 recognised, though merged into the surrounding colouring (two 

 or three which were kept alive in the Karlsruhe Zoological 

 Gardens had entirely lost this mark, as well as the darker spots 

 on the back) ; and I see that a Tropidonotus natrix caught on the 

 island of Oesel, off the Baltic provinces, was also without the 

 yellow patch on the neck.* The fact that this particular 

 'direction of variation' should be followed in localities so far 

 separated obtains in significance when regarded as a means of 

 producing that uniformity of tints above alluded to. 



On the other hand, the symmetrical rows of spots charac- 

 teristic of the young are by no means always disposed to become 

 less conspicuous. On the contrary, they frequently, by fusing 

 together, develop either into transverse or longitudinal lines, 

 which give the animal a marked appearance, and have led to the 

 formation of distinct varieties. Owing to their less stationary 

 habits, the varieties of snakes are locally not so restricted as 

 those of lizards often are, but, on the whole, it may be said that 

 the former set of varieties of natrix are more common to the 

 west of Europe, the latter to the east. 



I have not been able to determine satisfactorily the existence 

 of the melanic var. minax, Bonap., within the Grand Duchy. It 

 is found in the Alps, though not very abundantly (I have only come 

 across it three times), and in Bavaria, but not, I believe, elsewhere 

 in Germany ; and the many reports of " black" snakes in Baden 

 are perhaps due to the number of dark grey or brownish specimens. 

 Like the Blindworm, this species fluctuates in numbers from 



* Loewis, ' Eeptilien Kur-Liv und Esthlands.' 



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