320 
O LOSS ART, 
special organs for special work, 
as the specialization of the 
hand of man from the fore- 
foot of other mammals ; also 
applied to the special develop- 
ment during embryonic life of 
parts adapted for peculiar or 
special functions. 
Dig'it. a finger or toe. 
Di mid'i-ate. Half round. 
Di CE Ci-ous. (Gr. diSy two; 
oikos, house). With distinct 
sexes. 
Dip'te-ra (Gr. dis, two; pteron, 
wing). Two-winged flies ; an 
order of insects. 
Di yer-tic'u-lum. An offshoot 
from a vessel or from the ali- 
mentary canal. 
Duct. A tube or passage usu- 
ally leading from glands. 
Ec-dy'sts (Gr. ekdf/sis, casting 
oft'). The process of casting the 
skin ; moulting. 
E chin-o-deii'ma-ta (Gr. echinos, 
a hedgehog or urchin ; hence 
applied to the sea-urchin ; and 
derma, skin). The fourth sub- 
kingdom of animals. 
E-las-mo-bran'chm (Gr. elasma, 
a strap; hragchia, gill). The 
sharks and rays. 
E-la'ter. The spring or forked 
tail " of Podurans. 
E-ly'tra (Gr. elutron, a sheath). 
The fore-wings of beetles, 
serving to cover or sheathe the 
hind wings. 
Em'bry-o. The germ or young 
animal before leaving the egg 
or body of the parent. 
Endo-blast. The primitive, 
embryonic endoderm. 
En'te-ron (Gr. enteron). A gen- 
eral term applied to the diges- 
tive canal as a whole. 
E-phem'e-ri-na. The order of 
net veined insects represented 
by Ephemera. 
E'-Pi BLAST. The ectoderm in 
its embryo state. The ecto- 
blast. 
E piB o LE. Where the gastrula 
is formed by a spreading of a 
thin layer of epiblast cells 
over the much larger hypoblast 
cells. 
E-pis'to-ma. That part of the 
face of flies situated between 
the front and Ihe labrum. 
E QUI lat'e-ral. Having the 
sides equal, as in Brachiopod 
shells. 
E'qui-yalve. Applied to shells 
like the clams and most La- 
mellibranchs, which are com- 
posed of two equal pieces or 
valves. 
Ex skr'ted. Protruded; opposed 
to enclosed. 
Ex u'yi-um. Cast-off skin. 
Fis-sip'a-rous (Lat. fissus, cleft ; 
pario, to bring forth). Ap- 
plied to a form of asexual gen- 
eration where the parent splits 
into two parts, each part be- 
coming a new individual. 
Fce'tus. The embryo of a 
mammal. 
Gang'li-on (Gr. gagglion, a swell- 
ing or lump). A centre of 
the nervous system, consisting 
of nerve-cells and fibres. 
Gem-mip'a-rous {gemma, bud ; 
pario, to bring forth). Ap- 
