NOTODROMAS. 



[ 547 ] 



NUCLEUS. 



y. asa'dicola (PI. 19. fig. 22) resembles 

 Cyclops in general appearance. The ex- 

 ternal ovnry is a single organ, lying across 

 the back of the abdomen ; eye single ; 

 marine. 



•3 other species. 



BiBL. Allman, Ann. N. H. xx. 1 ; Baird, 

 Br. Enfom. 2;37 ; Bradv, Copep. i. 141. 



NOTOD'ROMAS, Lilljeborg.— An Os- 

 tracode related to Candona, among the Ct/- 

 pridce. It has long set?e on the lower an- 

 tennae, and two eyes. Its carapace has a 

 flat ventral surface with limiting ridges ; 

 and with this portion upwards it floats at 

 the top of sunny pools in Europe and the 

 British Isles (iV." monac/ms, Miiller), and in 

 Australia {N.fenesfrala, King). 



BiBL. BradV, Lijin. Tr. xxvi. 379. 



NOTOGO'NIA, Perty.— A gemis of Eu- 

 chlanidota (Rotatoria). 



Char. Lorica present, dilated posteriorly, 

 with two pointed processes on each side. 

 Eyes two, red; jaws curred, strong, with 

 two or three teeth ; caudal setae strong ; 

 between Confervcs. 



BiBL. Perty, Lehensf. 42. 



NOTOM'MATA, Eiir.— A gemis of Ro- 

 tatoria, of the family Hydatinaja. 



Char. Free ; eye single, cervical ; tail- 

 lilre foot with two toes ; rotatory organ 

 simply ciliated. 



In some the rotatory organ is extended 

 laterally in an ear- or arm-like form. 



Ehrenberg describes twenty-three species, 

 some of which are parasitic, N. petromyzon 

 and parasita living within Volvox glohutor^ 

 and N. Wernecldi within the vesicles of 

 Vaucheria ; and divides them into the sitb- 

 genera : — Labidodon, jaws each with a 

 single tooth ; Ctenodon, jaws each with 

 several teeth. 



Kotommata granularis is the male of N. 

 BracMonus. 



Many of the species are large and well 

 adapted for the study of the internal 

 structure. 



N. centrura (PI. 44. fig. 14 ; 1-5, jaws and 

 teeth). Body attenuate at each end, foot 

 small, and hard ; cephalic auricles short ; no 

 lateral -setae ; freshwater; length 1-36". 



BiEL. Ehr. Inf. 424; Duj. Inf. G4G ; 

 Pritchard, Infus.'GSl ; Hudson, M\ M. Jn. 

 1875. 



IsOTOXEC'TA, L. — A genus of aquatic 

 Hemipterous insects. 



The insects belonging to this genus have 

 the elytra membranous m the posterior part, 

 and the body is more or less boat-shaped. 



Fig. 530. 



Kotonec'ta glauoa. 

 Magnitied 3 diameters. 



The hind legs are very long, and when 

 stretched out resemble and act as a pair of 

 oars. The Notonectm swim on their backs, 

 and generally in a slightly inclined position, 

 on the surface of ponds and ditches. They 

 descend with great rapidity. They are 

 very voracious, and live on aquatic larvae, 

 biting also very sharply. Their mouth- 

 organs and limbs aiFord interesting micro- 

 scopic objects. 



N. glaiica (the water-boatman) is com- 

 mon in pools. 



NOTOPTEROPH'ORUS, Costa. — A 

 genus of Copepodous Entomostraca. Two 

 species ; marine. (Bradv, Copep. i. 141.) 



NUBECULA'RIA, Befrance.— An Im- 

 perforate Foraminifer ; shell bpaqite, often 

 sandy, protean, parasitic on shells and algae ; 

 straight, scale-hke, or cervicorn ; chambers 

 with imperfect base; at first spiral; aperture 

 oval, produced, often lipped. Fossil in the 

 Trias, Oolite, and Tertiaries; common in 

 shallow waters of warm latitudes (N.rugosa, 

 PI. 23. fig. 21). 



BiBL. Jones & Parker, Q. J. Geol. Soc. 

 xvi. 456 ; Carpenter, Eor. 69. 



NUCLEUS AND NUCLEOLUS of 

 Animals. See Cell, p. 138. 



NUCLEUS and NUCLEOLUS of 

 Plants. — The term nucleus is applied in 

 botany to two very diflerent things — first 

 to the central body of the young ovules of 

 Flowering plants, and secondly to a pecu- 

 liar structure met with in the interior of 

 cells. The first will be described under the 

 head of Ovule ; the cell-nucleus and nu- 

 cleolus are treated of in the article Cell, 

 Vegetable. 



Few parts of the minute organization of 

 plants are more obscure than the structure 

 and ftmction of nuclei : some authors re- 

 gard them as of the highest physiological 

 importance ; others consider their import 



2n2 



