Appendix 837 



Hymenoptera (hi men -op' tur a) (Gr. hymen, membrane; ptera, wings), order of 

 insects with membranous wings as bees, wasps, etc. 



Hyoid (hi'oid) (Gr. hyoides, Y-shaped), bone or cartilage at base of tongue. 



Hypersensitiveness (Gr. hyper, above), excessive sensitiveness to certain foreign 

 materials, especially proteins, because of peculiar permeability of mem- 

 branes. 



Hypertonic (hi per -ton' ik) (Gr. hyper, above; tension), possessing greater os- 

 motic pressure than some related substance (contrast with Hypotonic). 



Hypertrophy (hi -per' tro fi) (Gr. hyper, above; trophe, growth), excessive growth 

 or development (contrast with Atrophy). 



Hypha (hi' fa) (pleural, hyphae) (Gr. hyphe, web), a threadlike element of the 

 mycelium of a fungus. 



Hypnosis (hip -no' sis) (Gr. hypnos, sleep), type of artificially produced sleep in 

 which there are certain unusual activities, with the diminution or sus- 

 pension of others. 



Hypocotyl (hi po -kot' il) (Gr. hypo, below; hotyle, cotyledon), portion of the 

 embryo axis below the attachment of cotyledons and forming the primary 

 root of the seedling. 



Hypodermis (hi po -dur' mis) (Gr. hypo, below; derma, skin), cellular layer lying 

 below, and secreting, the cuticle of arthropods, annelids, and other in- 

 vertebrates. 



Hypostome (hi'postom) (Gr. hypo, under; stoma, mouth), around or under the 

 mouth. 



Hypotonic (hi po -ton' ik) (Gr. hypo, below; tension), possessing lesser osmotic 

 pressure than some other related substance (contrast with Hypertonic). 



Identical twins, those produced by the division of a single, fertilized egg and 

 resulting in two separate individuals with identical hereditary traits. 

 (Same as monozygous twins; contrast with Dizygotic or nonidentical 

 twins.) 



Ileum (il' e um) (L. ileum, groin), posterior or lower part of small intestine. 



Ilium (il' i um) (L. ilium, flank), dorsal part of hip or pelvic bone. 



Immunity (i -mu' ni ti) (L. im, not; munia, obligation), ability of an organism to 

 resist disease. 



Inbreeding, mating or crossing closely related types of animals or plants. 



Incisor (in -size' er) (L. incisis, cut), adapted for cutting. 



Incomplete dominance, neither of two genie factors completely dominating the 

 other. 



Indeterminate cleavage, segmentation of the egg in such a way that the pros- 

 pective fate of the individual cells is not easily traced, and consequently 

 there is very little specialization of the cells or blastomeres (contrast with 

 Determinate). 



Indirect cell division, see Mitosis. 



Individuality, in a living organism, consists of complex living protoplasm, some- 

 what limited in size, which possesses definite form, structure, chemico- 

 physical activities, and a certain degree of order, correlation, and sub- 

 ordination in order to bring about a unity of the whole. 



