508 GLOSSARY. 



Analogy. — That resemblance of structures wliicli depends upon 

 similarity of function, as in tlie wings of insects and birds. 

 Such structures are said to be be analogmis, and to be analog'ies 

 of each other. 



Animalcule. — A minute animal: generally applied to those visible 

 only by the microscope. 



Annelids. — A class of worms in which the surface of the body 

 exhibits a more or less distinct division into rings or segments, 

 generally provided with appendages for locomotion and with 

 gills. It includes the ordinary marine worms, the earth-worms, 

 and the leeches. 



Antenna. — Jointed organs appended to the head in Insects, Crusta- 

 cea and Centipedes, and not belonging to the mouth. 



Anthers. — The summits of the stamens of flowers, in which the 

 pollen or fertilizing dust is produced. 



Aplacentalia, Aplacentata or Aplacental Mammals. See Mam- 

 malia. 



Archetypal. — Of or belonging to the Archetype, or ideal primitive 

 form upon which all the beings of a group seem to be organ- 

 ized. 



Articui^ata. — A great division of the Animal Kingdom character- 

 ized generally by having the surface of the body divided into 

 rings called segments, a greater or less number of which are 

 furnished with jointed legs (such as Insects, Crustaceans and 

 Centipedes). 



Asymmetrical. — Having the two sides unlike. 



Atrophied. — Arrested in development at a very early stage. 



Balantjs. — The genus including the common Acorn-shells which 

 live in abundance on the rocks of the sea-coast. 



Batrachians. — A class of animals allied to the Reptiles, but under- 

 going a peculiar metamorphosis, in which the young animal is 

 generally aquatic and breathes by gills. {Examples, Frogs, 

 Toads and Newts.) 



Bowlders. — Large transported blocks of stone generally imbedded 

 in clays or gravels. 



Brachiopoda. — A class of marine Mollusca, or soft-bodied animals, 

 furnished with a bivalve shell, attached to submarine objects by 

 a stalk which passes through an aperture in one of tbe valves, 

 and furnished with fringed arms, by the action of which food is 

 carried to the mouth. 



Branchi.<51. — Gills or organs for respiration in water. 



Branchial. — Pertaining to gills or branchiae. 



Cambrian System. — A series of very ancient Palaeozoic rocks, 

 between the Laurentian and the Silurian. Until recently these 

 were regarded as the oldest fossiliferous rocks. 



Canid^.— The Dog-family, including the Dog, Wolf, Fox. Jackal, 

 etc. 



Carapace. — The shell enveloping the anterior part of the body in 



