700 GLOSSARY 



Pancreas. A digestive gland in the squid. 



Papulae. Delicate projections of the body-wall in the starfish. 



Paramylum. A granular substance resembling starch in Euglena. 



Parapodium. The appendage of annelids. 



Parasite. An animal which lives in or on another and feeds uj-'on its nutritive 

 fluids. 



Parenchyma. A vesicular connective tissue which fills the body-cavity of flat- 

 worms and leeches. 



Parietal Up. The side of the aperture of a snail shell towards the axis. 



Parietal tooth. A tooth on the parietal lip. 



Parthenogenesis. Eeproduction by means of unfertilized eggs. 



Paxillae. Calcareous rods surmounted by minute spines on the aboral surface 

 of certain starfish. 



Pedicellariae. Minute pincer-like organs present on the external surface of 

 certain echinoderms. 



Pedipalps. The second pair of appendages in arachinids. 



Peduncle. The stalk by which a sessile animal or a sessile organ is attached. 



Pen. The shell of the squid. 



Pericardium. The membrane surrounding the heart. 



Periopods. The thoracic appendages posterior to the maxillipeds in crusta- 

 ceans. 



Periostracum. The outer layer of the molluscan shell. 



Periphery. The outer surface of a body. 



Periproct. The region immediately around the anus. 



Perisarc. The cuticular outer covering of a hydroid. 



Peristome. A membrane surrounding the mouth in echinoderms; the outer 

 lip of the aperture of a snail shell. 



Peristomial gills. Gills on the peristome of sea-urchins. 



Peristomifum. The posterior portion of the head in most annelids. 



Peritoneum. The membrane lining the body-cavity. 



Peritreme. The stigmal plate in certain mites. 



Peronia. Thickenings of the ectoderm at the base of the tentacles in Narcome- 

 dusae. 



Petaloid area. The petal-like arrangement of the aboral ambulacral pores in 

 certain sea-urchins. 



Pharynx. The division of the alimentary tract immediately back of the mouth. 



Phragmocone. The chambered portion of the cephalopod shell. 



Pinnules. The small branches of the arms of crinoids. 



Plankton. A collective term referring to all small forms of life in the surface 

 waters of the sea or fresh water. 



Planula. The cilated free-swimming larva of many Cnidaria. 



Pleopod. An abdominal appendage in crustaceans. 



Plerocercoid. A tapeworm larva resembling the scolex of the adult worm. 



Plerocercus. A tapeworm larva consisting of the scolex and some of the pro- 

 glottids. 



Pleurobranch. A gill attached to the body-wall in crustaceans. 



Pluteus. The larva of a sea-urchin or a brittle star. 



Podia. The ambulacral appendages of echinoderms. 



Polinn vesicle. A sac projecting from the ring canal of echinoderms. 



Polymophism. The condition in which an animal species exists in several dis- 

 tinct forms. 

 Polyp. A sessile individual in Cnidaria or Bryozoa. 

 Posterior. At or towards the hinder end of an animal. 

 Proboscis. A prehensile organ in certain worms, usually a portion of the 



pharynx; the beakdike mouth-parts of certain arthropods. 

 Proglottid. A tapeworm segment. 



