GLOSSARY. 809 



PARTHENOGENESIS (Lat. parthenos, a virgin ; and gignomai, to be born). 

 Strictly speaking, confined to the production of new individuals from virgin 

 females by means of ova without the intervention of a male. Sometimes 

 used also to designate asexual reproduction by gemmation or fission. 



PATAGIUM (Lat. the border of a dress). Applied to the expansion of the in- 

 tegument by which Bats, Flying Squirrels, and other animals support 

 themselves in the air. 



PATELLA. The knee-cap or knee-pan. A sesamoid bone developed in the 

 tendon of insertion of the great extensor muscles of the thigh. 



PAUROPODA (Gr. pauros, little ; podes, feet). An order of Myriapoda. 



PECTINATE (Lat. pecten, a comb). Comb-like ; applied to the gills of certain 

 Gasteropods, hence called Pectinibranchiata. 



PECTORAL (Lat. pectus, chest). Connected with, or placed upon, the chest. 



PERENNIBRANCHIATA (Lat. perennis, perpetual ; Gr. Iragchia, gill). Applied 

 to those Amphibia in which the gills are permanently retained throughout 

 life. 



PEDAL (Lat. pes, the foot). Connected with the foot of the Mollusca. 



PEDICELLARL-E (Lat. pedicellus, a louse). Certain singular appendages found 

 in many Echinoderms, attached to the surface of the body, and resembling 

 a little beak or forceps supported on a stalk. 



PEDICLE (Lat. dim. of pes, the foot). A little stem. 



PEDIPALPI (Lat. pes, foot ; and palpo, I feel). An order of Arachnida com- 

 prising the Scorpions, &c. 



PEDUNCLE (Lat. pedunculus, a stem of stalk). In a restricted sense applied 

 to the muscular process by which certain Brachiopods are attached, and to 

 the stem which bears the body (capitulum) in Barnacles. 



PEDUNCULATE. Possessing a peduncle. 



PELAGIC (Gr. pelagos, sea). Inhabiting the open ocean. 



PELECYPODA (Gr. pelekus, an axe ; podes, feet). A name often applied to the 

 Lamellibranchiata, on account of many of them having a hatchet-shaped 

 or sickle-shaped foot. 



PELVIS (Lat. for basin). Applied, from analogy, to the basal portion of the 

 cup (calyx] of Crinoids. The bony arch with which the hind-limbs are con- 

 nected in Vertebrates. 



PERGAMENTACEOUS (Lat. pergamena, parchment). Of the texture of parchment. 



PERICARDIUM (Gr. peri, around ; kardia, heart). The serous membrane in 

 which the heart is contained. 



PERIDERM (Gr. peri, around ; and derma, skin). The hard cuticular layer 

 which is developed'by the coenosarc of certain of the Hydrozoa. 



PERIGASTRIC (Gr. peri, around ; and ff aster, stomach). The perigastric space 

 is the cavity which surrounds the stomach and other viscera, corresponding 

 to the abdominal cavity of the higher animals. 



PERIOSTRACUM (Gr. peri ; and ostrakon, shell). The layer of epidermis which 

 covers the shell in most of the Mollusca. 



PERIPLAST (Gr. peri; and plasso, I mould). The intercellular substance or 

 matrix in which the organised structures of a tissue are embedded. 



PERISARC (Gr. peri, around ; sarx, flesh). Employed by Prof. Allman as a 

 general term for the chitinous envelope secreted by many of the Hydrozoa. 



PERISOME (Qr.peri; and soma y body). The coriaceous or calcareous integu- 

 ment of the Echinodermata. 



PERISSODACTYLA (Gr. perissos, uneven ; daTctulos, finger). Applied to those 

 Hoofed Quadrupeds (Ungulata) in which the feet have an uneven number 

 of toes. 



PERISTOME (Gr. peri; and stoma, mouth). The space which intervenes be- 

 tween the mouth and the margin of the calyx in Vorticella ; also the space 

 between the mouth and the tentacles in a sea-anemone (Actinia) also the 

 lip or margin of the mouth of a univalve shell. 



PERIVISCERAL (Gr.peri; and Lat. viscera, the internal organs). Applied to 

 the space surrounding the viscera. 



PETALOID. Shaped like the petals of a flower. 



PHALANGES (Gr. phalanx, a row). The small bones composing the digits of the 

 higher Vertelrata. Normally each digit has three phalanges. 



