GLOSSARY. 585 



digits which normally compose the kind foot of a Vertebrate animal. In 



man, the great toe. 

 HALTERES (Gr. kaltcres, weights used by athletes to steady themselves in 



leaping). The rudimentary filaments or " balancers" which represent the 



posterior pair of wings in the Diptera, an order of Insects. 

 HAUSTELLATE (Lat. haurio, I drink). Adapted for sucking or pumping up 



fluids ; applied to the mouth of certain Crustacea and Jnsecta. 

 HECTOCOTYLUS (Gr. hekaton, a hundred ; kotulos, a cup). The metamor- 

 phosed reproductive arm of certain of the male Cuttle-fishes. In the 



Argonaut the arm becomes detached, and was originally described as a 



parasitic worm. 



HELMINTHOID (Gr. kelmins, an intestinal worm). Worm-shaped, vermi- 

 form. 

 HEMELYTRA (Gr. kemi, half; elutron, a sheath). The wings of certain insects, 



in which the apex of the wing is membranous, whilst the inner portion is 



chitinous, and resembles the elytron of a beetle. 

 HEMIMETABOLIC (Gr. kemi, half ; metabole, change). Applied to those Insects 



which undergo an incomplete metamorphosis. 

 HEMIPTERA (Gr. hemi ; and pteron, wing). An order of Insects in which the 



anterior wings are sometimes "hemelytra." 

 HERMAPHRODITE (Gr. Hermes, Mercury; Aphrodite, Venus). Possessing the 



characters of both sexes combined. 

 HETEROCERCAL (Gr. heteros, diverse ; kerkos, tail). Applied to the tail of 



Fishes when it is unsymmetrical, or composed of two unequal lobes. 

 HETEROGANGLIATE (Gr. heteros, diverse ; gagglion, a knot). Possessing a 



nervous system in which the ganglia are scattered and unsymmetrical (as 



in the Mollusca, for example). 



HETEROMORPHIC (Gr. heteros; morphe, form). Differing in form or shape. 

 HETEROPHAGI (Gr. lieteros, other ; pliago, I eat). Applied to Birds the young 



of which are born in a helpless condition, and require to be fed by the 



parents for a longer or shorter period. 

 HEXAPOD (Gr. hexa, six ; pous, foot). Possessing six legs ; applied to the 



Insecta. 

 HILUM (Lat. hilum, a little thing). A small aperture (as in the gemmules of 



sponges), or a small depression (as in Noctiluca). 

 HIRUDINEA (Lat. hirudo, a horse-leech). The order of Annelida comprising 



the Leeches. 

 HISTOLOGY (Gr. histos, a web ; logos, a, discourse). The study of the tissues ; 



more especially of the minuter elements of the body. 

 HOLOCEPHALI (Gr. holos, whole ; kephale, head). A sub-order of the Elasmo- 



branchii comprising the Chimcerce. 

 HOLOMETABOLIC (Gr. holos, whole ; metabole, change). Applied to Insects 



which undergo a complete metamorphosis. 

 HOLOSTOMATA (Gr. holos, whole ; stoma, mouth). A division of Gasteropodous 



Molluscs, in which the aperture of the shell is rounded, or "entire." 

 HOLOTHUROIDEA (Gr. holothourion ; and eidos, form). An order of Echinoder- 



mata comprising the Trepangs. 

 HOMOCERCUL (Gr. homos, same ; kerkos, tail). Applied to the tail of Fishes 



when it is symmetrical, or composed of two equal lobes. 



HOMOGANGLIATE (Gr. homos, like ; qagglion, a knot). Having a nervous sys- 

 tem in which the ganglia are symmetrically arranged (as in the Annulosa, 



for example). 

 HOMOLOGOUS (Gr. homos ; and logos, a discourse). Applied to parts which 



are constructed upon the same fundamental plan. 

 HOMOMORPHOUS (Gr. homos; and morphe, form). Having a similar external 



appearance or form. 



HUMERUS. The bone of the upper arm (brachium) in the Vertebrates. 

 HYALINE (Gr. hualos, crystal). Crystalline or glassy. 

 HYDATIDS (Gr. hudatis, a vesicle). The vesicle containing the larval forms 



(Echinococci) of the tapeworm of the dog. 

 HYDKAFORM. Resembling the common fresh-water polype (Hydra) in form. 



