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orthoenteric (or'thoe'n'te'rlk) a. 

 [Gk. orthos, straight ; enteron, in- 

 testine.] Having the alimentary 

 canal stretched out along the 

 ventral body surface ; appl. certain 

 Tunicates (zool.). 



orthogenesis (or'thoje'n'e'sis) n. [Gk. 

 orthos, straight ; genesis, descent.] 

 Variation which, irrespective of 

 natural selection or external forces, 

 gradually produces a new and dis- 

 tinct type (btol.). 



orthopterous (6rth8p'te"rus) a. [Gk. 

 orthos, straight ; pteron, wing.] 

 Having straight folded posterior 

 wings (zoo/."). 



orthospermous (or'thospeVmus) a. 

 [Gk. orthos, straight ; sperma, seed.] 

 With straight seeds (hot.). 



orthostichous (6rth6s'tlkus) a. [Gk. 

 orthos, straight ; stichos, a row.] 

 Appl. a fin skeleton when the peri- 

 pheral somactids are parallel as in 

 Cladoselache (pal.). 



orthostichy (orthos'Hk!) n. [Gk. 

 orthos, straight ;_ stichos, a row.] 

 The vertical line on which a row 

 of leaves or scales is found ; the 

 arrangement of the leaves or scales 

 in this row (bot.). 



orthotriaene (6r'th6tri'en) n. [Gk. 

 orthos, straight ; triaina, a trident.] 

 A triaene with cladi directed out- 

 wards at right angles to the shaft 

 (zool.). 



orthotropism (orthot'ropizm) n. [Gk. 

 orthos, straight ; trope, a turning.] 

 Growth in a vertical line (hot.*). 



orthotropous (orthSr/ropus) a. [Gk. 

 orthos, straight ; trope, a turning.] 

 Having the chalaza, hilum, and 

 micropyle in a straight line ; appl. 

 ovules (bot.). 



os (6s) n. [L. os, a bone.] A bone. 



osculant (os'kulant) a. [L. osculans, 

 kissing.] Closely adherent ; inter- 

 mediate in character between two 

 groups (btol.). 



oscular (os'kular) a. [L. osculum, a 

 small mouth.] Pert, an osculum. 



osculate (os'kulat) v. [L. osculare, to 

 kiss.] To have characters inter- 

 mediate between two groups (biol.). 

 osculiferous (6s'kullf6rus) a. [L. 

 osculum, a small mouth ; ferre, to 

 bear.] Having oscula (zool.). 

 osculum (Ss'kulum) n. [L. osculum, 



a small mouth.] An excurrent open- 

 ing in a Sponge (zool.). 



osmeterium (os'mgte'rium) n. [Gk. 

 osme, smell.] A forked protrusible 

 organ borne on the first thoracic 

 segment of the larva of many 

 butterflies, and emitting an offen- 

 sive smell (zool.). 



osmosis (osmo'sis) n. [Gk. othein, to 

 push.] A diffusion which takes 

 place between two miscible fluids 

 through a permeable membrane 



osmotic (SsmSt'ik) a. [Gk. othein, to 

 push.] Pert, osmosis (phys.). 



osphradium (osfra'dium) n. [Gk. 

 osphradion, strong scent.] A sense 

 organ associated with the visceral 

 ganglia in Molluscs, olfactory in 

 function (zool.). 



O88& triquetra, the Wormian bones 

 (anat.). 



ossein <(5s'eTn) n. [L. osseus, bony.] 

 The organic base of bone (phys.). 



osseous (os'eus) a. [L. osseus, bony.] 

 Composed of or resembling bone 

 (zool.). 



ossicle (fis'ikl) n. [L. os, bone.] Any 

 small bone ; one of those in the 

 sclerotic ; one of those in the 

 gastric mill of Crustacea ; a plate 

 of a sea-urchin's test (zool.). 



ossicular (Sslk'ular) a. [L. os, bone.] 

 Pert, ossicles. 



ossiculum (osik'ulum) n. [L. os, 

 bone.] An ossicle ; a lithodesma 

 (zool.} ; a pyrene (bot.). 



ossification (Sslfika'shun) n. [L. 

 os, bone ; facere, to make.] The 

 formation of bone ; the replace- 

 ment of cartilage by bone (anat.). 



ossify (os'tfi) v. [L. os, bone ; fieri, 

 to become.] To change to bone 

 (anat.). 



osteoblast (Ss'teoblast) n. [Gk. 

 osteon, bone ; blastos, bud.] A 

 bone-forming cell (smb.). 



osteoclast (Ss'teoklast) n. [Gk. osteon, 

 a bone ; klan, to break.] A cell 

 which absorbs or breaks up bony 

 tissue (entb.). 



osteocomma (os'teok8m'a) n. [Gk. 

 osteon, bone ; komma, piece.] A 

 segment of the vertebral skeleton 

 (zool.). 



osteocranium (6s'teokra'nlum) . 

 [Gk. osteon, bone ; kranion, skull.] 



