GLOSSARY. 



Alimentary Canal. — The digestire tube through which food passes ; 

 a simple tube in the simpler animals, bat differentiated into 

 several regions in the higher ones. The stomach region is re- 

 ' garded as its middle part, and is therefore sometimes spoken of 

 as the mid-gut, while the gullet region and the intestinal region 

 are distinguished respectively as the fore-gut and hind-gut. 



Alternation of Generations. — Some animals and plants have two 

 different forms, the one of which is developed in an asexual 

 manner from the other, while this in its turn is developed 

 sexually from the former. This cycle of alternating development 

 is called alternation of generations. See p. 150. 



Amoeblform (like an Amoeba). — A term applied to a cell capable of 

 changing its shape by pushing out pseudopodia and then re- 

 tracting them, as Amaba does. This is the primitive form of 

 the animal cell. (Amoeba, from Gk. dfjiei^u, to change ; for- 

 merly called the Proteus animalcule, from Proteus, the Greek 

 divinity, who possessed the power of changing his shape.) 



Analogous (Gk. dva\oyla, analogy), comparable. — An organ in one 

 kind of animal is said to be analogous with an organ in another 

 kind of animal when it fulfils the same uses. Thus the breath- 

 ing-tubes (trachete) of an insect are the analogue of the lungs 

 of a m.ammal ; they fulfil the same purpose, although derived 

 from a wholly different part of the body. 



Anatomy (Gk. dra and ro/i?}, cutting up). — The art of dissecting; 

 hence, the study of the parts of the body. Comparative anatomy, 

 the study of the way the parts of the body vary in different 

 animals, sometimes called morphology. 



Animalcule, pi. Animalcules (Lat. animalculwm, pi. animalcula, 

 diminutive of animal). — A name formerly given to the unicellular 

 organisms, and others too small to be seen without a microscope. 



Appendage. — This general term is applied to the many different 

 forms of legs and feelers borne by articulated animals. It is 

 useful, as'implying that they are all modifications of one general 

 type ; namely, that of a body-ring, bearing a pair of movable 

 organs, which may be jaws, antennfe, legs, gills, etc. 



Archenteron (Gk. ipx^- first, and Ivrefiov, see Entekon). — The primi- 



