_Distribution._--_Tropidonotus natrix_ occurs all over Europe, with, of course, the exception of Ireland, as far north as the extreme south-east of Scotland, and the sixty-fifth degree in Scandinavia and Finland, and as high up as 7,450 feet in the Italian Alps. With the exception of a few districts in England and in Central Europe, as well as in the extreme north, it is common everywhere, in the north as well as in the south. On the Mediterranean islands it is absent from the Baleares and Malta. In North Africa it is known from Algeria and Tunisia, north of the Atlas, where it does not seem, however, to be at all common. It has a wide range in Asia, extending eastwards to Lake Baikal, and southwards to Cyprus, Asia Minor, and Northern Persia. In the south-east of its range, the bilineated variety predominates over the typical form. The melanistic so-called varieties are not geographically restricted, but occur all over the habitat of the species, though not recorded from England. _Habits._--Although fond of water, and often seen swimming in ponds or streams or creeping by the water's edge, this snake is far less aquatic than its two congeners described hereafter; it often occurs on dry chalk hills or in woods far from any water. It is moderately agile in its movements, and easily caught, on which occasions it hisses loudly and emits a nauseous smell from its anal glands, together with the renal dejections, but makes no attempt to bite; exceptionally an individual may go so far as to strike with open mouth, but cases of this snake really biting are extremely rare. However, Gené says of the male of his _Natrix cettii_, "iracundum et mordacissimum animal." Dr. Gadow relates his experience with aggressive specimens which inhabited a swamp with a little stream to the north of Oporto, close to the coast. To his utter surprise, some of them actually made for him, swimming along rapidly with the head erect, about 6 inches above the water, and darting forwards with widely opened jaws; but they did not bite. According to Professor Kathariner, this snake when caught has been observed to sham death, lying rigid and motionless, with open gape. Some specimens do well in captivity, and are known to have lived for many years; others refuse all food and die of starvation. After a time they become tolerably tame, and cease to produce the offensive odour when handled.