Agamic

(Gr. a, without; gamos, marriage). Applied to all forms of reproduction in which the sexes are not directly concerned.

Allantoidea

The group of Vertebrata in which the foetus is furnished with an allantois, comprising the Reptiles, Birds, and Mammals.

Allantois

(Gr. alias, a sausage). One of the u membranes" of the foetus in certain Vertebrates.

Alveoli

(Lat. dim. of alvus, belly). Applied to the sockets of the teeth.

Ambulacra

(Lat. ambulacrum, a place for walking). The perforated spaces or " avenues" through which are protruded the tube-feet, by means of which locomotion is effected in the Echmodermata.

Ambulatory

(Lat. ambulo, I walk). Formed for walking. Applied to a single limb or to an entire animal.

Ametabolio

(Gr. a, without; metabole, change). Applied to those insects which do not possess wings when perfect, and which do not, therefore, pass through any marked metamorphosis.

Amnion

(Gr. amnos, a lamb). One of the foetal membranes of the higher Vertebrates.

Amniota

The group of Vertebrata in which the foetus is furnished with an amnion, comprising the Reptiles, Birds, and Mammals.

Amoeba

(Gr. amoibos, changing). A species of Rhizopod, so called from the numerous changes of form which it undergoes.

Amoebiform

Resembling an Amoeba in form.

Amorphozoa

(Gr. a, without; morphe, shape; zoon, animal). A name sometimes used to designate the Sponges.

Amphibia

(Gr. amphi, both; bios, life). The Frogs, Newts, and the like, which have gills when young, but can always breathe air directly when adult.

Amphicoelous

(Gr. amphi, at both ends; koilos, hollow). Applied to Vertebrae which are concave at both ends.

Amphidiscs

(Gr. amphi, at both ends ; diskos, a quoit or round plate). The spicula which surround the gemmules of Spongilla, and resemble two toothed wheels united by an axle.

Amphioxus

(Gr. amphi, at both ends ; oxus, sharp). The Lancelet, a little fish, which alone constitutes the order Pharyngobranchii.

Amphipneusta

(Gr. amphi, both; pneo, I breathe). Applied to the "perenni-branchiate " Amphibians which retain their gills through life.

Amphipoda

(Gr. amphi ; and pous, a foot). An order of Crustacea.

Anal

(Lat. anus, the vent). Connected with the anus, or situated near the anus.

Anallantoidea

The group of Vertebrata in which the embryo is not furnished with an allantois.

Analogous

Applied to parts which perform the same function.

Anamniota

The group of Vertebrata in which the embryo is destitute of an amnion.

Anarthropoda

(Gr. a, without; arthros, a joint; pous, foot). That division of Annulose animals in which there are no articulated appendages.