GLOSSARY. 317 



can be drawn across the eye in Birds and Reptiles, either to 

 moderate the effects of a strong light or to sweep particles of 

 dust, &c., from the surface of the eye. 



OcELLi._Xhe simple eyes or stemmata of Insects, usually situated 

 on the crown of the head between the great compound eyes. 



CEsopHAGUs.— The gullet. 



Oolitic— A great series of secondary rocks, so called from the 

 texture of some of its members, which appear to be made up 

 of a mass of small egg-like calcareous bodies. 



Opeeculum. — A calcareous plate employed by many MoUusca to 

 close the aperture of their shell. The opercular valves of Cir- 

 ripedes are those which close the aperture of the shell. 



Oebit. — The bony cavity for the reception of the eye. 



Oeganism. — An organised being, whether plant or animal. 



Oethospeemous.— A term applied to those fruits of the Umbel- 

 liferae which have the seed straight. 



Osculant. — Forms or groups apparently intermediate between and 

 connecting other groups are said to be osculant. 



Ova. — Eggs. 



OvAEiuM or OvAET (in plants).— The lower part of the pistil or 

 female organ of the flower, containing the ovules or incipient 

 seeds ; by growth after the other organs of the flower have 

 fallen, it usually becomes converted into the fruit. 



OviOEEous. — Egg-bearing. 



Ovules (of plants). — The seeds in the earliest condition. 



Pachydeems. — A group of Mammalia, so called from their thick 

 skins, and including the Elephant, Rhinoceros, Hippopotamus, 

 &c. 



Paleozoic. — The oldest system of fossiliferous rocks. 



Palpi. — Jointed appendages to some of the organs of the mouth in 

 Insects and Crustacea. 



Papilionacb*. — An order of Plants (see LEGUMjNOSiE). — The 

 flowers of these plants are c&Wedi papilionUeeous, or butterfly- 

 like, from the fancied resemblance of the expanded superior 

 petals to the wings of a butterfly. 



Paeasite. — An animal or plant living upon or in, and at the ex- 

 pense of, another organism. 



Paethenogenesis.— The production of living organisms from un- 

 impregnated eggs or seeds. 



