GLOSSAKY OF TECHNICAL TEEMS xxv 



HETEROSPOROUS (Gr. ere/oo?, different; airopos, seed), producing 



two kinds of spores. 

 HETEROSTYLED (Gr. erepos, different ; crruAoj, pillar), a term applied 



to certain plants (Primula) which produce two kinds of 



flowers, differing in the length of the style. 

 HETEROZYGOTE (Gr. erepo?, different ; fuycoro's, joined together), a 



Mendelian term applied to an organism produced by the 



union of two gametes which differ as regards some particular 



alternative character which they bear. 

 HEXADACTYLISM (Gr. ef, six; baKTvXos, finger), a condition in 



which six fingers or toes are present instead of the normal 



five. 

 HISTOLOGY (Gr. laros, web ; Ao'yos, discourse), the science which 



deals with animal and vegetable tissues or cell-aggregates. 

 HOLOPHYTIC (Gr. oAor, altogether ; </>uroV, plant), a term applied 



to the typical vegetable method of nutrition, by aid of 



chlorophyll. 

 HOLOZOIC (Gr. 6'Aoz/, altogether; fwor, animal), a term applied to 



the typical animal method of nutrition, by means of already 



elaborated food material. 

 HOMOLOGY (Gr. ojuoAoyia, agreement), essential structural identity 



due to community of descent. 

 HOMOPLASY (Gr. epos, the same ; TrAeWo), I mould), secondary 



resemblance due to similarity of habit. 

 HOMOSPOROUS (Gr. 6>oy, the same ; o--o'/>cs, seed), producing spores 



of one kind only. 

 HOMOZYGOTE (Gr. ojuoj, the same ; (yyuros, yoked), a Mendelian 



term applied to an organism produced by the union of two 



gametes which resemble one another as regards some par- 

 ticular alternative character which they bear. 

 HORMONE (Gr. op^v, that which sets in motion), an internal 



secretion which circulates in the body and acts as a stimulus. 

 HUMERUS (Lat. humerus), the bone of the upper arm. 

 HYBRIDISATION (Lat. hybrida, hybrid), the crossing of two distinct 



varieties or species by the union of the male gametes of the 



one with the female gametes of the other. 



HYDRA (Gr. vbpa, a water serpent), the common fresh-water polype. 

 HYDRANTH (Gr. vbpa, water serpent ; av6os, flower), a flower-like 



nutritive individual of a hydroid colony. 

 HYDROCAULUS (Gr. vbpa, water serpent ; KauAo's, stalk), the stem 



of a hydroid colony. 



