Although this singular perversion of the natural instincts of maternity sometimes occurs among the pigs which are allowed to roam together in herds, it seems to be far more common in those conditions where the animals are confined in pens without contact with their kind, and where they have no chance to recognize the young as members of their species or to acquire that interest in them which they would gain in the society of the herd. It is also clear that this maniacal habit is inherited; according to my observation it is common among the Berkshire, and relatively rare in other less specialized varieties. The intelligence of the pig is also shown in the readiness with which the creature changes its habits to meet varied environments. Thus the pigs which range the woods in the western and southern parts of the United States have learned to catch the crawfish which abounds in the shallow streams in those parts of this country. They will wade up a brook, turning over the stones and driftwood as they go, catching with a quick movement the crustaceans which they have thus dislodged from their cover. Along the shores of the Bay of Fundy, the pigs, accustomed to follow the tide out, picking the chance food which is thus exposed to them, have learned carefully to avoid the risk of being caught by the returning waters. With the first splash of the turning tide they hasten inshore until they have attained safe ground. One of the best evidences of the mental state of these animals is found in their actions when assailed by dogs or other beasts of prey. Pigs, though wary and sensible of danger, seem exempt from the extreme fear which leads to panic, and fight, even before being brought to bay by long chasing, in a discreet and valiant manner. Where a number of them are attacked by dogs or other enemies, they will form a circle with their heads out, each supporting the other in such a manner that the ring cannot readily be broken. Their thick-skinned forequarters and stout tusks provide them with excellent instruments with which to resist an assault. The sagacity of the pigs is probably, in part at least, to be attributed to the fact that in their native state they are communal animals, all the species of their family being accustomed to live gregariously, so that for ages they have had the training which every social organization, however simple, affords. They are, moreover, omnivorous feeders, accustomed to subsist on a great variety of food--a habit which seems in all cases to promote the development of the intelligence in animals.