370 PRINCIPLES OF ANIMAL BIOLOGY 



Ambystoma {am. his' to ma). A genus of salamanders. A. maculatum, A. tigrinum, 

 common species. 



Amino acid {am' i no). One of a number of organic acids containing the NHj radical 

 and having certain chemical properties. These acids enter into the composition 

 of all proteins and are produced by the splitting of proteins. 



Amitosis {a' mi to' sis). Cell division not involving the formation of chromosomes 

 or a spindle. 



Ammonite {am' mo nite). An extinct cephalopod having a coiled shell and com- 

 plicated foliaceous sutures; so called from the genus Ammonites. 



Amoeba {a me' ha). A genus of one-celled animals, a protozoon of the class Rhizop- 

 oda. 



Amphiaster {am' fi as' tcr). The figure produced by two asters and the connecting 

 spindle in a dividing cell. 



Amphibia. A class of Vertebrata embracing the frogs, toads, salamanders, and some 

 others. For definition see Chap. 19. 



Amphicoelous {am' fi see' lus). Having both ends of the centrum concave; said of 

 vertebrae. 



Amphineura {arn' fi nu' ra). A class of Mollusca, the members of which are bilater- 

 ally synunetrical, have a shell of eight pieces or no shell at all, and many pairs of 

 gills. Chiton is an example. 



Amphioxus. A primitive fishlike animal belonging to the subphylum Cephalochorda 

 of the Chordata. 



Amphiuma {am' fi u' ma). A genus of salamanders. 



Amylopsin (am' i lop' sin). A starch-digesting enzyme produced by the pancreas. 



Anabolism. The aggregate of constructive processes comprised in metabolism. 



Analogous {an al' o gus). Similar in function. 



Anaphase {an' a faze). Any stage of cell division during the passage of the chromo- 

 somes from the middle to the ends of the spindle. 



Anatomy. The science which treats of the structure of animals and plants as revealed 

 by dissection. It more commonly deals with the grosser features, but the finest 

 details of strvicture are not excluded. 



Anaximander {an aks' i man der). A Greek physical philosopher and mathematician, 

 pupil of Thales, who lived about 611-547 b.c. 



Animal pole. That part of an egg in which the protoplasm is concentrated (in eggs 

 with much yolk), and which in most animals produces the nervous system, sense 

 organs, etc. Other features may also characterize the animal pole. 



Anisogamete {an' i so gam' eet). One of two unlike cells which fuse in reproduction. 



Annelida {an neV i da). The phylum of animals comprising the segmented worms. 

 For definition see Chap. 19. 



Anodonta. A genus of fresh-water mussels. 



Antenna {an ten' na) {pi., antennae). One of a pair of jointed appendages project- 

 ing forward from the head of an insect or crustacean. 



Anthophysa (a?i' tho fi' za). A genus of colonial flagellate Protozoa whose cells are 

 borne in radiating masses on a branching stalk. 



Anthothrips niger {an' Iho Ihrips ni' jer). A species of insect of the order Thysan- 

 optera, commonly called thrips. 



Anthozoa {an' tho zo' a). A class of X'oelenterata, comprising the sea anemones and 

 most of the corals. They have no mcdusoid form in the life cycle. 



Anus {a' nus). The posterior oix-ning of the digestive tract. 



Apoda {ap' o da). An order of Amphibia comprising the legless forms called 

 caecilians. 



