These lizards take to the water to escape from their land enemies and not for food, a habit also known among certain other lizards, and one precisely the reverse of that of the Galapagos lizards. It would seem very probable that animals of such carnivorous habits as are the monitors might easily learn to capture water animals for food and thus eventually become aquatic in habit. This inclination toward, and partial adaptation to, water habits in the monitors is of much interest because in all probability the instinct is one of long inheritance from those remote ancestors which gave origin to the truly aquatic members of the order. Though the known geological history of the monitors does not extend far back, they are so intimately allied in their anatomical structure to the aquatic and semiaquatic lizards of Cretaceous times that there could seem to be no doubt of the common ancestry. _Dolichosaurs._—About fifty years ago Professor Owen, the famous English paleontologist, described a peculiar semiaquatic lizard from the Cretaceous rocks of England to which he gave the name _Dolichosaurus_, in allusion to the slender form of the body. Just what relations these slender lizards have to modern lizards has long been a problem; some have thought that they were their progenitors, but there are very good reasons for doubting this. No modern lizards, save the monitors, have more than eight vertebrae in the neck, while these dolichosaurs had as many as seventeen, a remarkable specialization for aquatic life that could hardly have been lost by their descendants. For this reason the dolichosaurs have usually been considered as representing a distinct suborder. But they have many resemblances otherwise to the monitors. They were semiaquatic in habit, and never more than six feet in length. They are yet imperfectly known, and no restoration of any form has hitherto been attempted. Their peculiar interest lies in the elongation of the neck, quite like that of the wholly unrelated nothosaurs and proganosaurs, which have been described in the foregoing pages. Doubtless similar habits in each had like results, but just what these habits were in the slender lizards we do not yet know.