306 MANUAL OP ZOOLOGY. 



PLANAKIDA (Gr. plane, wandering). A sub-order of the TurbeHaria. 

 PLAXOLA (Lat. planus, flat). The oval ciliated embryo of certain of the 



Hydrozoa. 

 PLATYELMIA (Gr. platus, broad; and helmins, an intestinal worm). The 



division of Scolecida comprising the Tape-worms, &c. 

 PLEURON (Gr. pleuron, a rib). The lateral extensions of the shell of 



Crustacea. 

 PXEUMATOCYST (Grr. pneuma. air; and kustis, cyst). The air-sac or float of 



certain of the Oceanic Hydrozoa (Phy&ophoricks). 

 PXEUMATOPHORE (Gr. pneuma, air; and phero, I carry). The proximal 



dilatation of the coenosarc in the Physophoridte, which surrounds the 



pneumatocyst. 

 PNETJMOSKELETON (Gr. pneuma ; and skeletos, dry). The hard structures 



which are connected with the breathing organs (e.g. the shell of Molluscs). 

 PODOPHTHALMATA (Gr. pous, foot ; and ophihalmos, eye). The division of 



Crustacea in which the eyes are borne at the end of long foot-stalks. 

 PODOSOMATA (Gr. pous, foot, soma, body). An order of Arachnida. 

 POLYCYSTINA (Gr. polus, many ; and kustis, a cyst). Aa order of Protozoa, 



with foraminated siliceous shells. 

 POLYGASTRICA (Gr. polus ; and gaster, stomach). The name applied by 



Ehrenberg to the Infusoria, under the belief that they possessed many 



stomachs. 

 POLYPARY. The hard, chitinous covering secreted by many of the 



Hydrozoa. 

 POLYPE (Gr. polus, many; pons, foot). Restricted to the single individual 



of a simple Actinozoon, such as a Sea-anemone, or to the separate zooids 



of a compound Actinozob'n, Often applied indiscriminately to any of the 



Ccelenterata, or even to the Polyzoa. 

 POLYPIDE. The separate zooid of a Polyzoon. 



POLYPIBOM. The dermal system of a colony of a Hydrozobn, or Polyzoon. 

 POLYPITE. The separate zooid of a Hydrozobn. 

 POLYSTOME (Gr. polus, many ; and stoma, mouth). Having many mouths ; 



applied to the Acinetce amongst the Protozoa. 

 POLYTHALAMOUS (Gr. polus', and thalamos, chamber). Having many 



chambers ; applied to the shells of Foraminifera and Cephalopoda. 

 POLYZOA (Gr. polus; and zobn, animal). A division of the Molluscoida, 



comprising compound animals, such as the Sea-mat. Sometimes called 



Bryozoa. 

 POLYZOARIUM. The dermal system of the colony of a Polyzoon ( = Poly- 



pidom). 



PORCELLANOUS. Of the texture of porcelain. 



PORIFERA (I at. porus, a pore; -dndfero, I carry). Sometimes used to desig- 

 nate the Foraminifera, or the Sponges. 

 POST-ANAL. Situated behind the anus. 

 POST-OSSOPHAGEAL. Situated behind the gullet. 

 POST-ORAL. Situated behind the mouth. 

 PRJE-OSSOPHAGEAL. Situated in front of the gullet. 

 PROBOSCIS (Lat. or Gr. the snout). Applied to the spiral trunk of Lcpido- 



pterous Insects, to the projecting mouth of certain Crinoids, and to the 



central polypite in the Medusa. 

 PROGLOTTIS (Gr. for the tip of the tongue). The generative segment or 



joint of a tape-worm. 



PRO- LEGS. The false abdominal feet of caterpillars. 

 PROPODIUM (Gr. pro, before; pous, foot). The anterior part of the foot in 



Molluscs. 



