GLOSSARY. 80; 



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, &c. 



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. 



ODONTOPHOEE (Gr. odous, tooth ; phero, I carry). The so-called " tongue " 

 or masticatory apparatus of Gasteropoda, Pteropoda, and Cephalopoda. 



ODONTOPTEEYX (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. 



OLIGOCH^ETA (Gr. oligos, few; chaite, hair). An order of Annelida, compris- 

 ing the Earth-worms, in which there are few bristles. 



OMASUM (Lat. bullock's-tripe). The third stomach of Kuminants, commonly 

 called the psalterium, or many -plies. 



OMNIVOROUS (Lat. omnia, everything ; voro, I devour). Feeding indiscrimi- 

 nately 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. 



OPERCULUM. A horny or shelly plate developed, in certain Mollusca, upon 

 the hinder part of the foot, and serving to close the aperture of the shell 

 when the animal is retracted within it ; also the lid of the shell of a Bala- 

 nus or Acorn-shell ; also the chain of flat bones which covers the gills iL 

 many fishes. 



OPHIDIA (Gr. ophis, a serpent). The order of Reptiles comprising the Snakes. 



OPHIDOBATRACHIA (Gr. ophis; batrachos, a frog). Sometimes applied to the 

 order of Snake-like Amphibians comprising the Ccecilice. 



OPHIOMORPHA (Gr. ophis; morphe, shape). The order of Amphibia compris- 

 ing the Ccecilice. 



OPHIUROIDEA (Gr. ophis, snake ; oura, tail; eidos, form). An order of Echino- 

 dermata comprising the Brittle-stars and Sand-stars. 



OPISTHOBRANCHIATA (Gr. opisthen, behind ; bragchia, gill). A division of 

 Gasteropoda, in which the gills are placed on the posterior part of the body. 



OpiSTHOCffiLOUS (Gr. opisthen, behind ; koilos, hollow). Applied to vertebrae 

 the bodies of which are hollow or concave behind. 



