They appear as pedunculated nodular tumors, with a smooth surface, usually reaching a large or enormous size. The substance of the tumor is composed of the dermoid tissue spoken of, formed into irregular masses of various size, form, color, and consistency, separated by connective-tissue fasciculæ and infiltrated with small and minute cysts (dilated glands or degenerated areas). The tumor is characterized by an atypical arrangement, form, and structure of the epithelium (after the type of a carcinoma) and an excessive growth of embryonal connective tissue (after the type of a sarcoma). It is extremely malignant, being destructive and distributed by metastasis and implantation. The cause of dermoid tumors of the ovary is unknown. Several different theories have been advanced, no one of which seems to be generally acceptable. PAROÖPHORITIC CYSTS, OR PAPILLOMATOUS OVARIAN CYSTS. There is an interesting variety of ovarian cysts which is characterized by the presence of papillomata, or warts, upon the inner surface. These cysts arise from the paroöphoron or from the hilum of the ovary. Many theories have been advanced to explain the origin of these tumors. Pathologists are far from agreeing upon this subject. Perhaps the most popular view among English and American pathologists is that the papillomatous cysts originate from the remains of the Wolffian body which may persist in the paroöphoron in various stages of degeneration. As paroöphoritic cysts spring from the hilum or the attached portion of the ovary, and develop in the direction of least resistance, they very often separate the lamellæ of the mesovarium and invade the loose connective tissue between the layers of the broad ligament. These cysts are thus very often extra-peritoneal or intra-ligamentous in their development. Some writers of experience state that three-fourths of all papillomatous tumors of the ovary are of intra-ligamentous growth. This has not been the experience of the author. The majority of the papillomatous ovarian cysts that he has seen have been intra-peritoneal in development, and have had as well-defined pedicles as the ordinary multilocular ovarian cyst. [Illustration: FIG. 168.--Papillomatous cyst of the paroöphoron. The section shows the papillomatous growths in the interior and the relation of the oöphoron.] _Cyst-wall._--If the papillomatous cyst be intra-peritoneal in development, two layers of tissue may be distinguished in its wall: an outer dense layer, composed of laminated connective tissue which sometimes contains unstriped muscle-fibers; and an inner loose layer of fibrous tissue. Both layers contain numerous blood-vessels. If the cyst be extra-peritoneal or intra-ligamentous in its development, we find, in addition to the two layers just described, an outer coat of peritoneum which is derived from the broad ligament.