Page:Popular Science Monthly Volume 4.djvu/283

Rh instincts peculiar to themselves, which are directly related to the necessities of their being; but we are not aware that they display great sagacity, cunning, or wisdom. They are not fertile in devices, not especially artful, and the extreme simplicity and smallness of their brain indicate their low mental powers.

The entire tribe of serpents for the purposes of this paper may be divided into the venomous and non-venomous species. Of the non-venomous, we will pass, with one or two remarks, the interesting families of double walkers, and slow or blind worms (Fig. 14), types which are structurally intermediate between true serpents and lizards. The first of these derives its name from the fact that it can progress



with facility forward or backward; the second from the erroneous notion that it has no eyes. To this class belong the curious glass-snakes, so named from their fragility. Other non-venomous serpents comprise the inoffensive and harmless, and some of the most terrible species. Of these we have noticed the gigantic rock-snake or python of India, which attains a length of 30 feet. The Natal rock-snake is found 25 feet long. Of equal size is the boa-constrictor of tropical America, formerly an object of worship. The anaconda, or water-serpent, which frequents the rivers of Brazil, and watches for its prey along their banks, is sometimes more than 25 feet long. These are