Introduction - Definition of terms and grouping. Causation of monstrosities. Nomenclature. I. Monstrosities by excess, in size or number. A. By excess in size, giants, local hypertrophies. B. By excess in number - Fission of embryo, i. Complete duplication, twins, with subsequent partial union (1) of xiphoid, (2) of thorax, (3) of thorax and head, (4) of head, (5) of pelvis, (6) of sacrum. II. Abcaudal duplication: (1) head single, and bodies equal; (2) head single, one body undeveloped and parasitic; (3) duplication of pelvis and legs. III. Abcranial duplication: (I) partial duplication of head - double-face; (2) complete division of head - double-head; (3) one division undeveloped and parasitic; (4) supernumerary arms. iv. Duplication both abcaudal and abcranial. v. Triple monsters. VI. Reduplication of parts. II. Monstrosities by defect in size or formation. A. Defect in size - Dwarfs. B. Defects in formation arising (1) from dropsy of the cerebro-spinal canal, etc.; (2) from influence of amnion, i. Extreme Defect in Twin-Fcetation. Acardiaci: (1) acephalus, (2) acormus, (3) amorphus. n. Defects involving the bead and spinal column: (1) Brain absent, Anencephalus; (2) brain displaced - Encephalocele, Hernia cerebri; (3) brain defective - Cyclopia; (4) jaw defective - Agnathia; (5) vertebral canal and cord imperfect - Spina bifida, III. Defective closure of parts in front: (1) facial clefts; (2) congenital fistula of neck; (3) defective closure of thorax; (4) of abdomen, iv. Defect of orifices and canals, v. Absence or defect of extremities. III Aberrant monstrosities, chiefly transposition of viscera.