GLOSSARY. 299 



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 'hemelytra.' 

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



the characters of both sexes combined. 

 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). 

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



Insecta. 

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



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

 HIRTJDINEA (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. 

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



which undergo a complete metamorphosis. 

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



podous Molluscs, in which the aperture of the shell is rounded, or 



' entire.' 

 HOI.OTHUROIDEA (Gr. holos ; thura, gate ; and eidos, form). An order of 



Echinodermata, comprising the Trepangs. 

 HOMOGANGLIATE (Gr. homos, like ; gagglion, a knot). Having a nervous 



system 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. 



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

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



(Eckinococci) of the tape-worm of the dog. 

 HYDRAFORM. Eesembling the common fresh-water polype (Hydra) in 



form. 

 HYDROCAULTIS (Gr. hudra, a water- serpent, and kaulos, a stem). The main 



stem of the ccenosarc of a Hydrozobn. 

 HYDROCYSTS (Gr. hudra; and Jcustis, a cyst). Curious processes attached 



to the ccenosarc of the Physophoridce, and termed 'feelers' (fuhler and 



taster of the Germans). 

 HYDROSCIUM (Gr. hudra ; and oikos, a house). The chamber into which the 



coenosarc in many of the Cah/cophoridcs can be retracted. 

 HYDROIDA (Gr. hudra; and eidos, form). The sub-class of the Hydrozoa, 



which comprises the animals most nearly allied to the Hydra, 

 HYDROPHYLLIA (Gr. hudra; and phyllon, a leaf). Overlapping appendages 



or plates, which protect the polypites in some of the Oceanic Hydrozoa 



( Calycophorida and Physophorida). They are often termed ' bracts,' and 



are the ' deckstucke ' of the Germans. 

 HYDRORHIZA (Gr. hudra ; and rhiza, root). The adherent base or proximal 



extremity of any Hydrozoon. 

 HYDROSOMA (Gr. hudra ; and soma, body). The entire organism of any 



Hydrozoon. 



