Dorsal

(Lat. dorsum, back). Connected with the back.

Dorsibranchiate

(Lat. dorsum, the back; Gr. bragchia, gill). Having external gills attached to the back ; applied to certain Annelides and Molluscs. The term is of mongrel composition, and " notobranchiate " is more correctly employed.

Ecderon

(Gr. ek, out; deros, skin). The outer plane of growth of the externa integumentary layer (viz., the ectoderm, or epidermis).

Ecdysis

(Gr. ekdusis, a stripping off). A shedding or moulting of the skin.

Echinococci

(Gr. echinos, a hedgehog; kokkos, a berry). The larval forms (scolices) of the tapeworm of the dog (Taenia echinococcus), commonly known as "hydatids."

Echinodermata

(Gr. echinos ; and derma, skin). A class of animals comprising the Sea-urchins, Star-fishes, and others, most of which have spiny skins.

Echinoidea

(Gr. echinos; and eidos, form). An order of Echinodermata, comprising the Sea-urchins.

Echinopaedium

(Gr. echinos, a hedgehog; paidion, a child). A term applied to the embryo or larva of the Echinodermata.

Echinulate

Possessing spines.

Ectocyst

(Gr. ektos, outside ; kustis, a bladder). The external investment of the coenoecium of a Polyzoon.

Ectoderm

(Gr. ektos; and derma, skin). The external integumentary layer of the Ccelenterata.

Ectosarc

(Gr. ektos; sarx, flesh). The outer transparent sarcode - layer of certain Rhizopods, such as the Amoeba.

Edentata

(Lat. e, without; dens, tooth). An order of Mammalia, often called Bruta.

Edentulous

Toothless; without any dental apparatus. Applied to the mouth of any animal, or to the hinge of the bivalve Molluscs.

Edriophthalmata

(Gr. hedraios, sitting; ophthalmos, eye). The division of Crustacea in which the eyes are sessile, and are not supported upon stalks.

Elasmobranchti

(Gr. elasma, a plate; bragchia, gill). An order of Fishes, including the Sharks and Rays.

Elytra

(Gr. elutron, a sheath). The chitinous anterior pair of wings in Beetles, which form cases for the posterior membranous wings. Also applied to the scales or plates on the back of the Sea-mouse (Aphrodite).

Embryo

(Gr. en, in; bruo, I swell). The earliest stage at which the young animal is recognisable in the impregnated ovum.

Enaliosauria

(Gr. enalios, marine; saura, lizard). Sometimes employed as a common term to designate the extinct Reptilian orders of the Ichthyosauria and Plesiosauria.

Encephalon

(Gr. egkephalos, brain). The portion of the cerebro-spinal nervous axis contained within the cranium.

Encephalous

(Gr. en, in ; kephale, the head). Possessing a distinct head. Usually applied to all the Mollusca proper, except the Lamellibranchiata.

Encystation

(Gr. en, in; kustis, a bag). The transformation undergone by certain of the Protozoa, when they become motionless, and surround themselves by a thick coating or cyst.