O LOSS ART, 
323 
CE-soph'a-gus (Gr. oisos, a reed ; 
phageia, to eat). The gullet. 
ON-TOG'E-NY(Gr. on, ontos, being; 
gene, birth). The development 
from the egg, of an individual 
animal. 
0-per'cu-lum (Lat. operio, to 
cover). In fishes one or more 
bones covering the gills ; in 
Gastropod moUusks a horny- 
plate or solid limestone mass 
closing the orifice of shells. 
0-pis-tho-cce'lous (Gr. opisthen, 
behind ; koilos, hollow). Those 
vertebrates with bodies hollow 
behind and convex in front. 
RAL. Related to the mouth. 
*R Ni tho-del'ph i-a (Gr. 07mis, 
bird ; delpJms, womb). The 
sub class of mammals and or 
der Monotremata. 
Or-thop'te-ra (Gr. orthos, 
straight ; pteron, wing). The 
order of insects with straight 
narrow fore-wings, as the grass- 
hoppers. 
Os-tra' CO-DA (Gr. ostracodes, 
shelled). A group of shelled 
Crustacea. 
O'to-liths (Gr. ous, ear ; lithos, 
stone). Small bones suspended 
in the internal ear of fishes, or 
concretions in the auditory 
sacs of invertebrates. 
0-vip'a ROUS (Lat. ovinn, an egg; 
pario, I bring forth). Applied 
to animals bringing forth eggs 
instead of living, active young. 
0-vi-POs'i-TOR (Lat. ovum, an 
egg; po7io, I place). An organ 
in insects homologous with the 
sting, by which eggs are de- 
posited in solid substances. 
O'vi-aAC. A sac or bag-like mem- 
brane attached to the parent, 
and containing eggs. 
0-vo-vi-vip'a-rous (Lat. ovum, 
an egg; vivus, alive; pario, I 
bring forth). Applied to such 
animals as retain their eggs in 
the body until they are hatched. 
DO gen'e-sis. Parthenoge- 
nous development in larval in- 
sects. 
Pal'lt-um (Lat. a cloak). The 
mantle or body-wall of mol- 
lusks, which secretes the shell; 
adj. pallial. 
Pa-pil'la. a minute soft projec- 
tion. 
Pa-ren'chyma (Gr. paregchuma, 
from para, en, chvo, something 
poured in besides). Applied 
to the proper substance of vis- 
cera, excluding connective tis- 
sue, blood-vessels, and other 
accessory parts. 
Par-the NO gen'e-sis (Gr. par- 
tlienos, virgin ; genesis, genera- 
tion). Reproduction by direct 
growth of germs from the egg, 
without fertilization by male 
germs or spermatozoa, as in the 
aphis, gall-insects, fiuke-worm, 
etc. 
Pel'a Gic. Living on the high 
seas, away from the coast; in 
mid-ocean. 
Per' I- SOME (Gr. peri, around; 
soma, body). In Crinoids the 
oral region of the cup or body. 
Per-en-ni-bran'chi-a-ta (Lat. 
perennis, perennial; hranchia, 
gill). Those Batrachia which re- 
tain their gills throughout life. 
Per-is-so dac'ty-la (Gr. perissos, 
uneven; daktulos, finger). 
