Why is the gecko so dangerous a reptile in houses?

Because it has a poisonous fluid between its scaly toes, which it communicates to the eatables over which it passes. It is common in Egypt, the East Indies, and the South Sea Islands, and even in some parts of Europe, as in the Kingdom of Naples.

Why do some lizards climb perpendicular walls, like the common house-fly?

Because they have suckers on the under side of the toes, the surfaces of which are broad. They consist of transverse pouches, with fringed margins.