666 GLOSSARY. 



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



man, the great toe. 

 HALTERES (Gr. halteres, 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 Insecta. 

 H?:CTOCOTYLUS (Gr. hekaton, a hundred ; kolulos, 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. helmins, an intestinal worm). Worm-shaped, vermi- 

 form. 

 HEMELYTRA (Gr. hemi, 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. hemi, 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. 

 HETEROCEROAL (Gr. hcteros, diverse ; kerkos, tail). Applied to the tail of 



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

 HETEROGANGLTATE (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. heteros, other ; phago, 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 ; andeidos, form). An order of Echinoder- 



mata comprising the Trepangs. 

 HOMOCERCAL (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 ; gagglion, a knot). Having a nervous sys- 

 tem in which the ganglia are symmetrically arranged (as in the A nnulosa, 



for example). 

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



are constructed upon the same fundamental plan. 

 HOMOMORPHOUS (Grr. 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. 

 HYDRAFORM. Resembling the common fresh-water polype (Hydra] in form. 



