The regeneration of the eye in triton was first made known by Bonnet. The right eye was partly cut out, and after two months it had completely regenerated. Blumenbach, in 1784, removed the anterior part of the bulb of the eye of “_Lacerta lacustris_.” Six months later a smaller bulb was present. Phillipeaux (’80) found that if the eye of an aquatic salamander was not entirely removed, a new eye regenerated; but if the eye was completely extirpated a new eye did not appear. Colucci, in 1885, described the regeneration of the lens of the eye of triton from the edge of the optic cup. Wolff, later, independently, discovered the same fact, and it has been more recently confirmed by E. Müller (’96), W. Kochs (’97), P. Rothig (’98), and Alfred Fischel (’98). The most important part of this discovery is that the new lens develops from the margin of the optic cup, and not from the outer ectoderm, as it does in the embryo. This result will be more fully discussed in a later chapter. It is highly probable in this case that the regeneration stands in no connection whatsoever with the liability of the eye to injury, for of the large number of salamanders that have been examined, none has been found with the eye mutilated. The position of the eye is such that it is well protected from external injury, and the tough cornea covering its outer surface would also further protect it from accidental injury. When we recall the high degree of structural complexity of the eye, its capacity to regenerate, if only a portion of the bulb is left, and its power to replace the lens if this is removed are certainly very remarkable facts. We find here, I think, an excellent refutation of the incorrectness of the general assumption of a connection between regeneration and liability to injury. Moreover, since there is no evidence whatsoever to show that the eyes in these animals are ever subject to diseases caused by bacteria, and much evidence to show that they are not so injured, we are still further confirmed in our general conclusion. It has been known for a long time that even in man the lens of the eye is sometimes regenerated after its removal. The regeneration has been supposed to take place from the old capsule of the lens, or possibly from a piece of the lens left after the operation; but whatever its origin, the fact of its regeneration in man, and in other mammals also, is a point of some interest in this connection.