=Am-blyp´o-da= [Gr. _amblys_, blunt; _pous_, foot.] An extinct order of ungulates having elephantine feet and whose navicular bone was supported by the cuboid. =Am-blys´to-ma= [Gr. _amblys_, blunt; _stoma_, mouth.] A genus of amphibians remarkable for the transformations they undergo. When undeveloped they represent the formerly recognized genus _Siredon_. Some species are called _axolotls_. =Am´i-a= [Gr. _amia_, a kind of tunny.] =Am-i-to´sis= [Gr. _a_-priv.; _mitos_, thread.] Direct cell-division; cell-division without the formation of nuclear figures. =Am´mon-ites= [Egyptian _Amon_.] Fossil cephalopod shells. =Am´nion= [Gr. _amnion_, fœtal membrane.] A membranous sack containing fluid which envelopes the embryo in the classes of reptiles, birds and mammals. =A-mœ´ba pro´te-us= [Gr. _amoibe_, change; Proteus.] A unicellular animal; a Protozoan. =Am-phib´i-a= [Gr. _amphi_, double; _bios_, life.] A class of vertebrates whose young are fish-like and have gills: the skull has two condyles and a parasphenoid. =Am-phi-mix´is= [Gr. _amphi_, double; _mixis_, mingling.] =Am-phi-ox´us= [Gr. _amphi_, double; _oxys_, sharp.] A small worm-like vertebrate whose body tapers at both ends. The skeleton is notochordal; skull, brain, auditory, and renal organs are absent. =An-ab´o-lism= [Gr. _ana_, up; _ballo_, throw.] Constructive metabolism; the series of chemical changes by which a cell builds up simple and stable food into the highly complex and unstable living material. =An-ap-to-mor´phus= [Gr. _an_-priv.; _hapto_, fasten; _morphe_, shape.] =An-gi-o-sper´mæ= [Gr. _angeion_, vessel; _sperma_, seed.] Plants whose seeds are contained in a closed seed-vessel. =An-nu-la´ta= [Lat. _annulatus_, ringed.] A division of Vermes, including marine worms, leeches, and earthworms. =An-the-rid´i-a= [NL., < _anthera_, anther; Gr. dim. _idion_.] The male sexual organ in cryptogams answering to the anthers in phanerogams. =An-thro-po-pi-the´cus= [Gr. _anthropos_, man; _pithekos_, ape.] =An´thro-poid= [Gr. _anthropos_, man; _eidos_, form.] Manlike: said especially of the gibbons, orangs, gorillas, and chimpanzees. =An-ti-tox´ine= [Gr. _anti_, opposed to; _toxikon_, poison.] =A-nu´ra= [Gr. _an_, not; _oura_, tail.] An order of amphibians without a tail in the adult, including the toads and frogs. =A´phis= [Gr. _apheideis_, lavish.] In Entomology a genus typical of Aphididæ. An aphid; a plant-louse. =Ap-pen´dix ver-mi-for´mis= [Lat. _appendo_, to hang from; _vermis_, worm; _forma_, form.] A vestigial structure attached to commencement of the large intestine. =A-rach´ni-da= [Gr. _arachne_, spider.] A class of Arthropods embracing the spiders, mites, scorpions, etc. =Ar-cel´la= [Lat. dim. _arca_, a box.] Belonging to a group of protozoans having a chitinous shell. =Ar-chæ´an= [Gr. _archaios_, ancient.] Pertaining to the oldest strata of rocks in geological history.