Rhesus Macaque (_Macacus rhesus_). Glandular hyperplasia of prostate. The bladder is collapsed. The opening of the urethra is occupied by a firm, friable yellow-white cast of matter apparently inspissated semen. Urethral mucous membrane normal. Prostate is 7 × 4.5 × 3 cm. firm, resilient, dull purple-gray, capsule negative. Section shows normal lobulations containing apparently normal secretion. Vasa negative. Testes negative. Microscopic section of prostate shows acini of various sizes lined by a single layer of tall vacuolated cells with nucleus at the bottom. Cells probably nowhere reduplicated. Acini nowhere grossly atypical but everywhere hyperplastic and dilated irregularly. Mass is adenomatous in general increase but no part is truly neoplastic. Interstitial tissue rather less than normal proportionately. No “amyloid” bodies. [Illustration: FIG. 30.—PAPILLARY ADENOMATOUS HYPERPLASIA OF THE PROSTATE GLAND. RING TAILED LEMUR (LEMUR CATTA). ] Still another case of accessory sex gland enlargement was found in a Ring tailed Lemur (_Lemur catta_), this time, however, with more suggestion of a neoplastic change. The prostate of the lemur is normally large, pale gray-pink and rather firm. Histologically it is about equally glandular and fibrous. In this case the cellular activity is undoubted, and one must consider it adenomatous. The cause of death was enteritis, being perhaps more serious in the presence of the urethral obstruction. The seminal vesicles are distended to 7 × 2 cm. with a thick boiled- starch-like material. Wall and mucosa are negative. Prostate large, tense and injected. Its cut surface is pale purple, homogeneous; character of fluid is normal although excessive. Urethra is occupied by a cast of rather tenacious starch-like matter which begins at neck of bladder and runs almost to meatus. Openings of excretory ducts are prominent. Mucosa and submucosa of urethra are deep purple and the former seems to be slightly opaque as if covered with desquamated epithelium. Testes and epididymes seem normal. Vasa deferentia are slightly distended with excess of normally turbid fluid. Microscopical section shows hyperplastic epithelial condition with accumulation of droplets of hyaline matter but there is no amyloid deposit. In places it is possible to see a hyperplastic and loosened epithelium with nuclei becoming vacuolated, and the whole being cast off. Less granular free globules suggest that this is the method of origin of the hyaline globules free in the acini. The picture is one of papillary adenoma. In some places there is surely reduplication of the lining cells. Connective tissue is deeply staining, compact and with adult nuclei. Growth is not very vascular. There are no corpora amylacea.