Nucleated

Possessing a nucleus or central particle.

Nucleolus

1. The minute solid particle in the interior of the nucleus of some cells. 2. The minute spherical particle attached to the exterior of the "nucleus" or ovary of certain Infusoria, performing the functions of a testicle.

Nucleus

(Lat. nucleus, a kernel). 1. The solid or vesicular body found in many cells. 2. The solid rod, or band-shaped body found in the interior of many of the Protozoa, and having, in certain of them, the functions of an ovary. 3. The "madreporiform tubercle" of the Echinodermata. 4. The embryonic shell which is retained to form the apex of the adult shell in many of the Mollusca.

Nudibranchiata

(Lat. nudus, naked; and Gr. bragchia, gill). An order of the Gasteropoda in which the gills are naked.

Nymphs

The active pupae of certain Insects.

Occipital

Connected with the occiput or the back part of the head.

Oceanic

Applied to animals which inhabit the open ocean (= pelagic).

Ocelli

(Lat. diminutive of oculus, eye). The simple eyes of many Echino-derms, Spiders, Crustaceans, Molluscs, etc.

Octopoda

(Gr. octo, eight; pous, foot). The tribe of Cuttle-fishes with eight arms attached to the head.

Odontoceti

(Gr. odous, tooth; ketos, whale). The "toothed" Whales, in contradistinction to the "whalebone" Whales.

Odontoid

(Gr. odous; eidos, form.) The "odontoid process" is the centrum or body of the first cervical vertebra (atlas). It is detached from the atlas, and is usually anchylosed with the second cervical vertebra (axis), and it forms the pivot upon which the head rotates.

Odontophore

(Gr. odous, tooth; phero, I carry). The so-called " tongue" or masticatory apparatus of Gasteropoda, Pteropoda, and Cephalopoda.

Odontopteryx

(Gr. odous, tooth; pterux, wing). An extinct genus of Birds.

Odontornithes

(Gr. odous, tooth; ornis, bird). The extinct sub-class of Birds comprising forms with distinct teeth in sockets.

OEsophagus

The gullet or tube leading from the mouth to the stomach.

Oligochaeta

(Gr. oligos, few; chaite, hair). An order of Annelida, comprising the Earth-worms, in which there are few bristles.

Omasum

(Lat. bullock's-tripe). The third stomach of Ruminants, commonly called the psalterium, or many-plies.

Omnivorous

(Lat. omnia, everything; voro, I devour). Feeding indiscriminately upon all sorts of food.

Onychophora

(Gr. onux, claw or nail; phero, I carry). The order of which Peripatus, with its hooked feet, is the type.

Oocysts

(Gr. oon, egg; kustis, bladder). Chambers appended to the cells of certain of the Polyzoa, which serve as a receptacle for the eggs. Sometimes called "ovicells."

Operculata

(Lat. operculum, a lid). A division of pulmonate Gasteropoda, in which the shell is closed by an operculum.