OTOLITHS. 



[ 564 ] 



OVARY. 



Char. Eyes three ; one sessile and cervi- 

 cal, the two others stalked and frontal; 

 neither jaws nor teeth present. 



O. papillosa. Body campanulate, turgid, 

 rough with papillae; freshwater ; length 

 1-96". 



BIBL. Ehr. Inf. 453; Pritchard, Inf. 690. 



O'TOLITHS. The crystalline or crys- 

 talloid particles found in the labyrinth of 

 the internal ear. They are enclosed in sacs, 

 appearing as white specks ; and are com- 

 posed of carbonate of lime, with an organic 

 basis, which is left after the action of dilute 

 acetic acid. 



OTONYS'SUS, Kol. A genus of Sar- 

 coptidse (Anoplura). O.sticlwlasius, on the 

 bat ; other species. (Maddox, M. Mic. Jn. 

 1871, 144; Murray, EC. Ent. 317.) 



OTOS'TOMA, Carter. A genus of Holo- 

 trichous Infusoria. 



Char. Ovoid, mouth ear-shaped; anus 

 terminal ; nucleus long ; contractile vesicles 

 double. Its cysts have been discovered on 

 Nitella, and give exit to monadiform beings 

 approaching the parent shape. 



O. Carteri, Bombay. 



BIBL. Carter, Ann. N. H. 1866, xvii. 117; 

 Kent, Inf. 500. 



OVA OF ANIMALS. The germs secretad 

 by the ovaries. When extruded from the 

 body, they are generally termed eggs (Eo-GS). 

 See OVUM. 



OVARY. The organ in which the ova 

 or germs of the future offspring are formed 

 and temporarily contained. 



The ovary consists of an outer fibrous 

 capsule, and a parenchyma or stroma. 



Transverse section ol' a human ovary at the fifth 

 month of pregnancy, a, Graafian vesicle of the under, 

 b, of the upper surface ; c, peritoneum ; d, the tunica 

 albuginea; in the centre are two corpora lutea; e, 

 stroma of the ovary. 



Tta outer coat, or tunica albuginea, is 

 firm, white, and intimately connected with 



the subjacent stroma: it consists of inter- 

 lacing bundles of connective tissue with 

 few elastic fibres. 



A layer of columnar or germ-epithelium 

 covers the capsule, therefore different from 

 that of the peritoneum, with which it is 

 continuous at the base of the organ. The 

 germ-epithelium here and there lines tube- 

 like inward prolongations (the ovarian 

 tubes). 



The stroma (fi*. 538 e) is composed of 

 nucleated connective tissue, and in it are 

 imbedded the Graafian vesicles (fig. 538 a). 

 They vary greatly in number and size ; the 

 largest are generally nearest the surface, and 

 project more or less, so as to give it a nodu- 

 lar aspect. They are round closed sacs 

 (tig. 539J. Each possesses two coats ; the 



Fig. 539. 



G-raaflan vesicle of the pig. a, outer, b, inner layer 

 of the fibrous coat; c, membrana granulosa; d, liquid 

 contained in the vesicle ; e, proligerous disk ; f, ovum 

 with the zona pellucida, yolk, and germinal vesicle. 



Magnified 10 diameters. 



outer is a fibrous and vascular layer, con- 

 nected with the stroma by somewhat lax 

 areolar tissne, which consists of two layers : 

 the outer composed of ordinary fibrous con- 

 nective tissue; the inner consisting of young 

 connective tissue, rich in cells, usually fusi- 

 form, stellate, or spheroidal, and resembling 

 amoeboid cells. Lining this is the epithe- 

 lium of the follicle, which covers the whole 

 of the inside of the tunica propria, and 

 forms the membrana granulosa (fig. 539 c). 

 Next the surface of the ovary this is 

 thickened and projects in wards, "forming the 

 proligerous disk, e ; the epithelium is strati- 

 fied and columnar. The ovum is imbedded 

 in this proligerous disk. 



The cavity of the Graafian vesicle con- 

 tains a liquid resembling the serum of the 

 blood ; and in it are found granules, nuclei, 

 and cells, arising from the disintegration of 

 the membrana granulo'sa. 



When the vesicle bursts, the ovum es- 



