GLOSSARY. 273 



Eocene. The earliest Tertiary epoch. 



Ephippium. The case in which the winter eggs of the Daphniidse 



are deposited. 

 EphyriK, The disk-like segments which gradually fall off from 



the "hydra-tuba" of certain Hydrozoa, growing often to a large 



size, and developing organs. 

 Epiblast in the embryo is the ectoderm in the adult ; in the 



higher animals the latter becomes the epidermis. 

 Epiboly. An occasional form of growth in the embryo (the epi- 



blast over the hypoblast). 

 Epiccele. The " perivisceral cavity " of the Ascidians and Ver- 



tebrata. 



Epidermis. The outer skin or cuticle of the higher animals. 

 Epigenesis. The doctrine that organic development depended 



upon the juxtaposition of molecules according to " the opera- 

 tion of a developmental force." 

 Epiglottis. A cartilaginous valve placed in front of the larynx 



which it closes when in the act of swallowing. 

 Epimera. Lateral pieces of the thorax placed behind the epi- 



sterna. 

 Epiphragm. The calcareous secretion of the foot in snails, 



closing the aperture of the shell during hibernation. 

 Epiphyses. The separately ossified ends of a long bone. 

 Epipleura. The sides of the elytra in Coleoptera, they are not 



commonly marked off from the dorsal portion. 

 Epipodia. Appendages of the foot in some Mollusca. In the 



Pteropoda they are wing-like expansions from the head. 

 Epipodite. A process of the basal joint of the legs in certain 



Crustacea. 

 Episterna. Lateral pieces of the thorax, above or outside the 



cotyloid cavities in the Arthropoda. 

 Epistoma. The part, not always apparent, connecting the upper 



lip to the clypeus in the mandibulate insects, or the part above 



the mouth generally. In the Crustacea it seems to answer to 



the clypeus. In the Polyzoa it is a lip or valve placed over 



the mouth of the polypide. 

 Epitheca. A continuous external layer of the thecce of the coral- 



lites in some of the Zoantharia. 



Epithelium. The thin membrane that covers the mucous mem- 

 branes. 



