SIERRA DE V IN ALES 239 



the circulation of a victim, is one of the most in- 

 teresting problems in biology. There are, for 

 instance, certain families among the Ophidians 

 that include genera of both venomous and of non- 

 venomous snakes. The fact that a development 

 of the poison glands took place in widely differing 

 genera and in distant parts of the world, quite inde- 

 pendently of each other, would indicate that snakes, 

 as a type of animal life, possess a tendency in that 

 direction. If, therefore, the poison apparatus is 

 of benefit to so many kinds of snakes, and all have 

 a tendency to its development, why have so many 

 orders of them no such provision? It is probably 

 true that the majority of non-poisonous species 

 are the more active snakes relying more upon alert- 

 ness and agility to meet their life requirements, 

 while the reverse is generally the case with the 

 poisonous ones that depend upon their specialized 

 poison equipment to protect themselves. There 

 are exceptions, however, as in the case of the king 

 cobra of India, and to a lesser degree in the fer-de- 

 lance of Martinique. Among the snakes of our 

 own country, one cannot fail to contrast the slug- 

 gish sedentary habit of our pit vipers with the 

 nervous agility of the harmless forms. As a mat- 



