Protoplasm

(Gr. protos; and plasso, I mould). The elementary basis of organised tissues. Used synonymously with the "sarcode" of the Protozoa.

Protopodite

(Gr. protos, first; and pous, foot). The basal segment of the typical limb of a Crustacean.

Protozoa

(Gr. protos; and zoon, animal). The lowest division of the animal kingdom.

Proventriculus

(Lat. pro, in front of; ventriculus, dim. of venter, belly). The cardiac portion of the stomach of birds.

Proximal

(Lat. proximus, next). The slowly-growing, comparatively-fixed extremity of a limb or of an organism.

Psalterium

(Lat. a stringed instrument). The third stomach of Ruminants.(See Omasum.)

Pseudembryo

(Gr. pseudos, falsity; embruon, embryo). The larval form of an Echinoderm.

Pseudobranchia

(Gr. pseudos, falsity; bragchia, gill). A supplementary gill found in certain fishes, which receives arterialised blood only, and dots not, therefore, assist in respiration.

Pseudohaemal

(Gr. pseudos, falsity; and haima, blood). Applied to the vascular system of Annelida. Pseudo - hearts. Certain contractile cavities connected with the atrial system of Brachiopoda, and long considered to be hearts.

Pseudo-navicellae

(Gr. pseudos, false; and Navicula, a genus of Diatoms).

The embryonic forms of the Gregarinidae, so called from their resemblance in shape to the Navicula.

Pseudopodia

(Gr. pseudos; and pous, foot). The extensions of the body-substance which are put forth by the Rhizopoda at will, and which serve for locomotion and prehension.

Pseudova

(Gr. pseudos; Lat. ovum, egg). The egg-like bodies from which the young of the viviparous Aphis are produced.

Pteropoda

(Gr. pteron, wing ; and pous, foot). A class of the Mollusca which swim by means of fins attached near the head.

Pterosauria

(Gr. pteron, wing ; saura, lizard). An extinct order of reptiles.

Pubis

(Lat. pubes, hair). The share-bone ; one of the bones which enter into the composition of the pelvic arch of Vertebrates.

Pulmogasteropoda

(=Pulmonifera).

Pulmonaria

A division of Arachnida which breathe by means of pulmonary sacs.

Pulmonate

Possessing lungs.

Pulmonifera

(Lat. pulmo, a lung; and fero, I carry). The division of Mollusca which breathe by means of a pulmonary chamber.

Pupa

(Lat. a doll). The stage of an insect immediately preceding its appearance in a perfect condition. In the pupa-stage it is usually quiescent - when it is often called a "chrysalis;" but it is sometimes active - when it is often called a "nymph."

Pylorus

(Gr. puloros, a gatekeeper). The valvular aperture between the stomach and the intestine.

Pyriform

(Lat. pyrus, a pear; and forma, form). Pear-shaped.