Charles Darwin: The Origin of Species by means of Natural Selection

GLOSSARY 1. GLOSSARY OF THE PRINCIPAL SCIENTIFIC TERMS USED IN THE PRESENT VOLUME. (continued)

HOMOLOGY.--That relation between parts which results from their development from corresponding embryonic parts, either in different animals, as in the case of the arm of man, the fore-leg of a quadruped, and the wing of a bird; or in the same individual, as in the case of the fore and hind legs in quadrupeds, and the segments or rings and their appendages of which the body of a worm, a centipede, etc., is composed. The latter is called serial homology. The parts which stand in such a relation to each other are said to be homologous, and one such part or organ is called the homologue of the other. In different plants the parts of the flower are homologous, and in general these parts are regarded as homologous with leaves.

HOMOPTERA.--An order or sub-order of insects having (like the Hemiptera) a jointed beak, but in which the fore-wings are either wholly membranous or wholly leathery, The Cicadae, frog-hoppers, and Aphides, are well-known examples.

HYBRID.--The offspring of the union of two distinct species.

HYMENOPTERA.--An order of insects possessing biting jaws and usually four membranous wings in which there are a few veins. Bees and wasps are familiar examples of this group.

HYPERTROPHIED.--Excessively developed.

ICHNEUMONIDAE.--A family of hymenopterous insects, the members of which lay their eggs in the bodies or eggs of other insects.

IMAGO.--The perfect (generally winged) reproductive state of an insect.

INDIGENES.--The aboriginal animal or vegetable inhabitants of a country or region.

INFLORESCENCE.--The mode of arrangement of the flowers of plants.

INFUSORIA.--A class of microscopic animalcules, so called from their having originally been observed in infusions of vegetable matters. They consist of a gelatinous material enclosed in a delicate membrane, the whole or part of which is furnished with short vibrating hairs (called cilia), by means of which the animalcules swim through the water or convey the minute particles of their food to the orifice of the mouth.