272 GLOSSARY. 



Ectostosis. Ossification proceeding from without to within. 



Elytra. The upper or anterior wing-cases of the Coleoptera. 

 The term is also applied to the scales on the back of certain 

 Annelida. 



Embolium. A part of the corium in the hemelytra of certain 

 Hemiptera. 



Emboly. " Invagination," the formation of a cavity in the 

 embryo. 



Embryo. The animal in the egg or in the womb ; but it is also 

 sometimes applied to the young larva. " We look at the em- 

 bryo as a picture, more or less obscured, of the progenitor, 

 either in its adult or larval states, of all the members of the 

 same great class." 



Embryology. The study of the embryo. 



Empodium. That part of the last tarsal joint in insects to which 

 the claws are attached. 



Enamel (Encaustum). The hardest constituent, when it exists, 

 of the tooth. 



Endoderm (hypoblast of the embryo). The inner tegumentary 

 layer of the Metazoa. 



Endoplast. The probable analogue, according to Huxley, in the 

 Protozoa of the nucleus of the Metazoa. 



Endopleurite. That part of the apodema of a Crustacean which 

 arises from the interepimeral membrane. 



Endopodite. An inner filamentous appendage attached to the 

 basal joint of some of the Crustacea. 



Endosarc. The inner layer of sarcode in the Protozoa. 



EndosJceleton. The internal hard or bony structure. 



Endosternite. That part of the apodema of a Crustacean that 

 arises from the intersternal membrane. 



Endosteum. The vascular tissue lining the medullary cavity of 

 the long bones. 



Endostoma. A part behind the labrum in the Crustacea. 



Endostyle. The longitudinal fold in the pharynx of Ascidians. 



Enterocode. The " perivisceral cavity " of the Echinoderms, 

 Mollusca, &c. 



Environment. "The totality of all surrounding agencies and in- 

 fluences " (Mivart). " A term of the most comprehensive 

 kind, embodying, in every case that it is used, an assemblage 

 of conditions presenting an amount of complexity that is not 

 only inconceivable but wholly unnanieable " (Romanes). 



