The remote ancestors of the vertebrates possessed a median, unpaired, myolonic eye, which was subsequently replaced in function by the evolution of the paired eyes. The cyclopic condition occurs very frequently among human monstrosities, much more frequently than among animals, Hannover claims,[206] but this is clearly due to the fact that human monstrosities are much more frequently recorded. Of the 120 cases I have been able to collect from literature, 56 presented other evidences of degeneracy than cyclopic conditions, and 60 had neuropathic or other taint in the ancestry. Dareste[207] has shown that the production of a single eye, the changes in the structure of the mouth, the atrophy and abnormal situation of the olfactory apparatus and of the vesicle of the hemispheres, all result from an arrest of development. The determining influence must be exerted very early in the life history of the embryo. [Illustration: FIG. 33.] Hannover points out that there often is coincident hydrocephalus and harelip, imperfect genital development, and allied arrest of development. J. R. Folsom, of Cecil, Georgia, has reported a female, born alive to a negro multipara, who died two hours after birth. The eye was centrally located in the forehead, on a line with the nose. The brow was a complete arch, as was the upper eyelid. The lower lid had a mark midway, indicating an attempt at division. The nasal bones were wanting, but the soft part of the nose, destitute of the orifice, hung over the mouth, which was completely covered. The chin was recedent. C. Phisalix described a case in which the nose was wanting. Its place in the median was occupied by a single eye; on the horizontal diameter were two pupils separated by a narrow space. Landolt, discussing a case reported by Valude, points out that in cyclopic eyes all the parts may be double or united in every degree except that there is never a single lens or double vitreous. Bock and others, however, describe cases in which the eye has not been formed by the conglomeration of two separately developed eyes, but it is a single developed eye; the other being wanting entirely. Bruce reports a cyclop in which there was a single socket for the eye of a lozenge-shape, situated in the lower middle of the forehead. The socket was furnished with two pairs of eyelids, upper and lower. The eye was found to consist of two rudimentary eyes, with two rudimentary retinæ, apparently springing from a single optic vesicle. The nose was represented by a short process attached to the forehead, above the median eye. [Illustration: FIG. 34.] The cyclops illustrated (Figs. 33, 34) was born to a 17-year old neuropathic primipara, after a protracted labour. The child was living, but was killed by pressure on the funis. The mouth contained an ivory, tusk-like tooth at each corner. There was mane-like hair around the neck.