WIN- 



349 



XEN- 



wing coverts, see tectrices. 



wing pad, the undeveloped wing of 



insect pupae (zool.). 

 wing petal, the lateral petal in 



papilionaceous plants (dot.). 

 winter egg, the egg of many fresh- 

 water forms provided with a thick 

 shell which preserves it as it lies 

 quiescent during the winter ; cf. 

 summer eggs (zoo I.). 

 wisdom teeth, the four molar teeth 

 which complete the permanent set 

 in man, erupting much later than 

 the others (anat,). 



wolf tooth, a small premolar tooth 

 at the front' of the premolar series, 

 occasionally present in Horses 

 (zool.). 



Wolfflan (wool'flan) a. \_Wolff, em- 

 bryologist.] Afipl. certain structures 

 first discovered by Wolff. 

 Wolfflan body, the embryonic meso- 

 nephros which arises bythedevelop- 

 ment of a series of mesonephnc 

 tubules (anat.). 



Wolffian duct, the duct of the 

 mesonephros : this may arise either 

 by a splitting of the pronephric 

 duct, or it may be the whole of the 

 pronephric duct (anat.). 

 Wolfflan ridges, ridges which appear 

 on either side of the middle line of 

 the early embryo, and upon which 

 the limb-buds are formed (emb.). 

 wood (wood) n. [A.S. wudu, wood.] 

 The hard substance of a tree stem, 

 the xylem of the vascular bundles 

 (hot.}. 



wood cell, one of the special cells 

 in the xylem of a vascular bundle 

 (hot.}. 

 wood fibres, sclerenchymatous 



fibres (bot.). 

 wood parenchyma, lignified paren- 



chymatous cells (bot.). 

 wood vessel, an element of tracheal 

 tissue, a long tubular structure 

 formed by cell-fusion (bot.). 

 Woolner's tubercle, see Darwinian 



tubercle (zool.). 

 worker, a non-fertile female in a 



colony of social Insects (zool.). 

 worm (wurm) n. [A.S. ivyrm, worm.] 

 A general name of no scientific 

 value, used to designate any of 

 the Flatworms, Roundworms, Poly- 

 chaetes or Oligochaetes (zool.). 



Wormian bones (wor'mlan), see 



sutural bones, 

 wrist bones, the name applied to 



the bones that go to make up the 



carpus (zool.). 



xanthin (zan'thln) n. [Gk. xanthos> 

 yellow.] Yellow colouring matter 

 in flowers (bot.). 



xanthine (zan'thm, zan'then) n. [Gk. 

 xanthos, yellow.] Dioxy-purine, 

 found in muscle, liver, pancreas, 

 and in urine ; also in certain plants 



xanthocarpous (zan'thokar'pus) a. 

 [Gk. vanities, yellow ; karpos^ fruit.] 

 Having yellow fruits (bot.). 



xanthodont (zan'thodSnt) a. [Gk. 

 xantfwS) yellow ; odous, tooth.] 

 Having yellow-coloured incisors ; 

 appl. certain Rodents (zool.). 



xanthophane (zan'thofan) n. [Gk. 

 xanthos, yellow ; phainein, to 

 appear.] Chromophane. 



xanthophyll (zan'thofil) n. [Gk. 

 xanthos, yellow ; phyllon, leaf.] A 

 yellow colouring matter found in 

 autumn leaves, probably a con- 

 stituent of chlorophyll (bot.). 



xanthopous (zan'thopiis) a. [Gk. 

 xanthos, yellow ; pous, foot.] Hav- 

 ing a yellow stem (bot.). 



xanthospermous (zan'thospeVmus) a. 

 [Gk. xanthos, yellow ; sperma, seed.] 

 Having yellow seeds (bot.). 



xenarthral (ze'nar'thral) a. [Gk. xenos, 

 strange ; arthron, joint.] Having 

 additional articular facets on the 

 dorso-lumbar vertebrae (zool.). 



xenia (ze'nta) n. [Gk. xenios, hospit- 

 able.] Appearances in the seed 

 of characters, after cross-fertiliza- 

 tion, belonging to foreign pollen 

 parent (bot.). 



xenogamy (ze'nSg'aml) n. [Gk. xenos, 

 strange ; gamos, marriage.] Cross- 

 fertilization (bot.). 



xenogenesis (zgn'6j6n'6sls) n. [Gk. 

 xenos, strange ; gigneslhai, to pro- 

 duce.] Heterogenesis (biol.). 



xenomorphosis (ze'n'om&r'fosTs) n. 

 [Gk. xenos, strange ; morphe^ shape.] 

 Heteromorphosis. 



