Mammæ are found in various degrees of development. In some cases there are present one or more tags of skin resembling a nipple. In others the mammæ may be well formed and may contain glandular tissue. The bones appear as delicate laminæ or spiculæ in the cyst-wall. They often present a striking resemblance to the flat bones of the skull and the jaw-bones. The contents of a dermoid cyst vary in consistency. All the substances discharged from the lining membrane enter into their composition. They may consist of a thick oily fluid of a yellowish or brown color, or a pultaceous, semi-solid mass. They resemble the contents of a wen or a sebaceous cyst. They are usually filled with loose hairs and exfoliated epithelium. Though the fatty contents may be in a fluid condition during life, yet they solidify when exposed to the air and after death. In some cases a dermoid cyst has been found in one ovary while a glandular cyst was in the other. Again, a single ovary may be the seat of a mixed tumor composed of dermoid and glandular cysts. In most of such cases the dermoid forms a single loculus of the tumor. Sometimes the septum between the dermoid cavity and the glandular cystic cavity atrophies and the two cavities are thrown into one. Such an occurrence explains those cases in which the cavity of a multilocular cyst is found to be partly lined with skin which is continuous with the cylindrical epithelium characteristic of the glandular cyst. The sebaceous glands and the sweat-glands in the walls of an ovarian dermoid may become obstructed and undergo cystic degeneration, forming in this way groups of secondary cysts. Dermoid cysts of the ovary are usually intra-peritoneal in their growth, like the glandular cysts. In some cases, however, they develop between the layers of the broad ligament, and may assume any of the positions characteristic of such extra-peritoneal growths. _Teratoma_, a very rare form of ovarian tumor, is an atypical modification of the dermoid, the teratoma bearing a relation to the dermoid similar to that of carcinoma to adenoma. While in the dermoid the chief mass of the tumor has a cystic character, the cystic cavity containing the secretions from the lining epidermal tissue, the teratoma is for the most part a solid tumor, and the productive activity of the tissue is a cellular hyperplasia.