GLOSSARY. 303 



NEMERTIDA (Gr. Nemertes, proper name). A division of the Turbellarian 

 Worms, commonly called ' Ribbon-worms.' 



NERVURES (Lat. nervus, a sinew). The ribs which support the membranous 

 wings of insects. 



NEURAL (Gr. neuron, a nerve). Connected with the nervous system. 



NEUROPODIUM (Gr. neuron, a nerve ; pous, the foot). The ventral or inferior 

 division of the ' foot- tubercle ' of an Annelide ; often called the ' ventral 

 oar.' 



NEUROPTERA (Gr. neuron ; and pteron, a wing). An order of Insects, cha- 

 racterised by four membranous wings with numerous reticulated nervures 

 (e.g. Dragon-flies). 



NEUTER (Lat. neither the one nor the other). Having no fully developed 

 sex. 



NOTOBRANCHIATA (Gr. notos, the back ; and bragchia, gill). Carrying the 

 gills upon the back ; applied to a division of the Annelida. 



NOTOPODIUM (Gr. notos, the back, and pous, the foot). The dorsal division 

 of one of the foot-tubercles or parapodia of an Annelide ; often called 

 the ' dorsal oar.' 



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 in- 

 terior of many of the Protozoa, and having, in certain of them, the func- 

 tions of an ovary. 3. The ' madreporiform tubercle ' of the Echinoder- 

 mata. 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 pupse of certain Insects. 



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. 

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



or masticatory apparatus of Gasteropoda, Ptcropoda, and Cephalopoda. 

 ([ESOPHAGUS. The gullet or tube leading from the mouth to the stomach. 

 OncocH/iiTA (Gr. oligos, few ; chaitc, hair). An order of Annelida, com- 

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

 OPERCULATA (Lat. opercidum, a lid). A division of pulmonate Gasteropoda, 



in which the shell is closed Vy 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 



Ealanus or Acorn-shell. 

 OPHIUROFDEA (Gr. ophis, snake; our a, tail; eidos, form). An order of 



Echinoderm-ata, comprising the Brittle-stars and Sand-stars. 

 OPISTHOBRAXCHIATA (Gr. opisthon, behind ; bragchia, gill). A division of 



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



body. 

 ORAL (Lat. os, mouth). Connected with the mouth. 



