Appendix 815 



Amnion (am' ni on) (Gr. amnos, lamb; the membrane around the embryo), thin 

 membranous sac enclosing the embryos of reptiles, birds, and mammals. 



Amoeboid (a -me' boid) (Gr. amoibe, to change), resembling an Amoeba. 



Amphiaster (am fi -as' ter) (Gr. amphi, both; aster, star), the figure formed in 

 dividing cells by the two asters and the spindle. 



Amphibious (am -fib' i us) (Gr. amphi, both; bios, life), living both in water 

 and on land. 



Amphiblastula (am fi -bias' tu la), free-swimming larval stage of sponges. 



Amphimixis (am fi -mik' sis) (Gr. amphi, both; mixis, mingling), a union of 

 nuclear materials from two different cells, as in fertilization. 



Amphoteric (am fo -ter' ik) (Gr. amphi, both), partaking of the nature of both, 

 as proteins have both acid and basic properties. 



Ampulla (am-pul'a) (L. ampulla, flask), saclike structure of the ambulacral sys- 

 tem of starfishes. 



Amylase (am' i las) (Gr. amylon, starch; «5^/enzyme), starch-splitting enzyme. 



Amylopsin (am i -lop' sin) (Gr. amylon, starch), a starch-splitting enzyme of the 

 pancreatic juice. 



Anabolism (an ab' o lizm) (Gr. anabole, to build), the building-up phase of me- 

 tabolism. 



Anaerobe (an-a'erob) (Gr. an, without; aer, air), living without free oxygen 

 (contrast with aerobe). 



Anal (a' nal) (Gr., anus, anus), pertaining to the anus. 



Analogy (analogous) (a-nal'ogi) (Gr. ana, according to; logos, proportion), 

 organs structurally different which perform similar functions, as wings of 

 birds and butterflies. 



Anaphase (an'afaz) (Gr. ana, up; phasis, appear), stage in mitosis in which 

 chromosomes move toward the poles of the cell. 



Anaphylaxis (an a fi -lak' sis), the reaction to foreign protein material which has 

 a toxic effect and which may be due to increased sensitivity to the mate- 

 rial because of previous contact with it. 



Anastomose (a -nas' to moz) (Gr. anastomosis, join), to join together into a net- 

 work such as blood vessels. 



Anatomy (a-nat'omi) (Gr. ana, up; temno, to cut), structure of organs, espe- 

 cially as revealed by dissection. 



Angiosperm (an' ji o spurm) (Gr. angio, covered; sperm, seed), plants with seeds 

 enclosed by carpels (contrast with Gymnosperm). 



Animal pole, that part of a cell in which the protoplasm has the highest rate 

 of metabolism in contrast with the vegetal pole. 



Anion (an' ion) (Gr. ana, up; ienai, to go), a negatively charged particle or ion 

 that travels to the positive anode during electrolysis. 



Annelida (a-nel'ida) (L. annulus, ring), with ringlike segments as in the earth- 

 worm. 



Annual (an' u al) (L. annus, year), plants which complete their life cycle and 

 die within one year. 



Annular ring, ringlike structure in stems of higher plants which show seasonal 

 growth. 



Antenna (an -ten' a) (Gr. ana, up; teino, stretch), jointed sensitive organ on the 

 head of insects, Crustacea, etc. 



