OVOTESTICULAR 



954 



OXALETHYLIN 





plasm]. The protoplasm of the unimpregnated ovum 

 or ovicell. 



Ovotesticular (p-vo-tes-tik' -u-lar) \yov, ovum, egg ; 

 testis, testicle]. Pertaining to an Ovotestis. 



Ovotestis (o-vo-tes' -tis) \y6v, ovum, egg ; testis, testicle : 

 pi. , Ovotestes~\. In biology, a generative organ produc- 

 ing both male and female products ; an ovispermary, 

 as seen in opisthobranchiate Branchiogasteropoda. 



Ovoviviparity (p-vo-vi-vip-ar' '-it-e) [Mv, ovum, egg; 

 viviparus, bringing forth alive]. The character of 

 being ovoviviparous. 



Ovoviviparous (o-vo-vi-vip' '-ar-us) [<t>6v, ovum, egg ; 

 viviparus, bringing forth alive]. In biology, repro- 

 ducing by means of eggs incubated within the body, 

 as distinguished from oviparous and viviparous. 



Ovula (o' ' -vu-lah) [L.]. Plural of Ovulum. O. of 

 Naboth. See Ovule. 



Ovular, Ovulary (o'-vu-lar, o' -vu-lar-e) [o!<6v, ovum, 

 egg]. Relating to an ovule or ovum. 



Ovulate (o'-vu-lat) [ovulum, a little egg]. In biology, 

 to produce ovules or discharge them from the ovary. 

 Ovuliferous. 



Ovulation (o-vu-la' -shun)\ovulum, dim. of ovum, egg]. 

 The maturation and escape of the ovum. 



Ovule (p'-vul) \yov, ovum, egg]. In biology : (a) A 

 small ovum or animal egg ; (^)a young or rudimentary 

 seed. O., External Migration of, the transfer of an 

 ovule from the right ovary to the left oviduct, or from 

 the left ovary to the right oviduct. O., Membrana 

 granulosa of, the layer of stratified follicular epithe- 

 lium lining the cavity of the ovisac. The prominence 

 formed at one side is called the cumulus ovigerus, 

 or discus proligerus. O., Migration of, the transfer 

 of the ovule from the ovary to the oviduct. O. of 

 Naboth, one of the small cysts resulting from obstruc- 

 tion of the ducts of the glands of the cervix of the 

 uterus. O., Polar Cells of, certain cells thrown off 

 upon the surface of the vitellus of the unimpreg- 

 nated ovum. O., or Cell, Primordial, one of the 

 primitive ovules in the substance of the ovary. O., 

 Tunica granulosa of, the layer surrounding the 

 ovum. 



Ovuliferous {o-vu-lif -er-us) [ovulum, a little egg; an 

 ovule; ferre, to bear]. In biology, ovule-bearing. 



Ovuligerous (o-vu-li; y -er-us). Same as Ovuliferous. 



Ovulist (o ; -vu-list) [<s>6v, ovum, an egg]. In biology, 

 an adherent of the doctrine of incasement, q. v. ; an 

 ovist. 



Ovulum (o'-vu-lum) [L. : pi., Ovula]. An ovule. 

 See Ovule. 



Ovum (o'-vum) [u6v, ovum, an egg: pi. , Ova~\. In 

 biology, the female reproductive cell of an animal ; the 

 egg. It consists of protoplasm (the yolk), and a nucleus 

 (the germinal vesicle) in the unfertilized ovum. It is 

 either naked or covered by one or more membranes 

 and envelops, which either originate from the egg itself, 

 constituting real primary yolk or egg-integuments, or 

 from the surrounding parietal tissues, constituting sec- 

 ondary or accessory egg-envelops. Ova arise in special 

 organs of the metazoan body called ovaria or germaria. 

 The nucleus or germinal vesicle {yesicula germinativa) 

 is of relatively great size, and central or peripheral in 

 situation. It consists of a distinct membrane and an en- 

 closed nuclear fluid, in which lie one or more solid 

 nucleoliox germinal spots {macula germinativa:), which 

 may be connected by an intranuclear network of fine 

 threads. The protoplasm consists of fine, firm particles, 

 forming the threads and meshes of a fine network, the 

 spongioplasm, within which is the more fluid hyaloplasm. 

 This constitutes the formative yolk, besides which 

 there is frequently present nutrient material in the form 

 of drops of fat or oil, and small plates or spheres which 



form the deuteroplasm, or nutritive yolk. This is rarely 

 absent ; usually it is present in considerable quantity. 

 Eggs are distinguished as (A) Alecithal, in which the 

 food-yolk is entirely absent, or present only in very 

 small quantity. (B) Telolecithal, in which the food- 

 yolk and the formative yolk divide the egg into two 

 hemispheres, called respectively the vegetative and the 

 animal ; or in which the quantity of the nutritive yolk is 

 greatly in excess, the formative yolk being but a seg- 

 ment or mass at the animal pole, in which lies the germ- 

 inal vesicle. In both cases a thin layer of protoplasm 

 spreads over the entire surface of the ovum. (C) 

 Centrolecithal, in which the formative yolk is ar- 

 ranged in a regular layer around the whole ovum, as 

 well as in a mass at the center of the ovum in which 

 lies the germinal vesicle. The region between the 

 central and the peripheral formative yolk is more or 

 less completely occupied by deuteroplasm. The distri- 

 bution of formative yolk and food-yolk affects the germ- 

 inative phenomena. When the food-yolk is scant and 

 more or less thoroughly intermingled with the forma- 

 tive yolk, germination is accompanied by a practically 

 uniform segmentation and the egg is called holoblastic, 

 e.g., as in all mammals except monotremes, and in 

 some invertebrates, e.g., spiders. When the formative 

 yolk and the food-yolk are separated into more or less 

 well-defined masses, the segmentation is less symmetric 

 and uniform and is called meroblastic. The egg en- 

 velops are divided into: (i) Primary etwelops, yolk- 

 membranes ; these are sometimes double, perforated by 

 numerous pores (zona radiata) and occasionally there is 

 a special opening, the micropyle. (2) Secondary acces- 

 sory envelops, some of which are formed by the ovum 

 itself. O., Apoplectic, one the seat of a hemorrhagic 

 extravasation. O., Blighted, an impregnated ovum 

 the development of which has been arrested by disease 

 or by hemorrhage into the chorion or amniotic cavity. 

 O. -cycle, an ovum-product. O., Male, certain cells 

 found in diverticula of the seminiferous tubules, 

 considered to be rudimentary or imperfect spermato- 

 zoa. O., Meroblastic, an ovum with a large amount 

 of food-yolk which takes no active part in the devel- 

 opment of the embryo. O., Permanent, the fully 

 developed ovum capable of being fertilized. O., Pri- 

 mordial. See Egg-cells. O. -product, the whole 

 product of an ovum. 



Owen's Fissures. See Fissures, Table of. O.'s Line. 

 See Lines, Table of. 



Ox (oks) [ME., oxe, ox]. The adult male of the Bos 

 taurus ; a bull. O.-acid. Same as Oxyacid. O.- 

 bile. Same as O.-gall. O.-eyed, having large, full 

 eyes. O.-fly, the bot-fly (Hypoderma bovis), which 

 infests cattle. O.-foot, in farriery, the hind foot oj 

 a horse when the horn cleaves just in the middle ot 

 the fore part of the hoof from the coronet to tin- shoo. 

 O.-gall. See Fcl bovis. O. -warble, a fly trouble- 

 some to cattle ; also called heel-fly. See Hypoderma 

 bovis under Parasites (Animal), Table of. 



Oxalantin (oks-al-an' '-tin) [b%vc, acid ; Ger. , 



elecampane], C fi H 6 N 4 O fi . Leukoturic acid; an acid 

 obtained by the action of zinc and HC1 upon oxalyl 

 urea. It occurs in crystalline crusts, sparingly soluble 

 in water. 



Oxalate (oks'-al-at) [b£a?,lc, sorrel]. Any salt of oxalic 

 acid. In the plural, the term usually refers to calcium 

 oxalate, which is found in the urine under certain con- 

 ditions. 



Oxalemia (oks-al- e'-me- ak) [Italic, sorrel; a\ua, 

 blood]. Excess of the oxalates, or of oxalic acid, in 

 the blood. 



Oxalethylin (oks-al-eth f -il-in) [offc, acid ; alOi/p, ether ; 

 vln, matter], C„H, n N,,. An oily liquid boiling at 



