GLOSSARY 211 



Ductus ejaculatorius : the terminal portion of the male reproductive tract in 

 insects, 17. 



Ectoderm : the outermost layer of cells in the Cnidaria and Spongiaria ; 



Hydra, 160 ; tubularians, 165 ; campanularians, 171. 

 Ectosarc : the outermost layer of non-granular protoplasm in protozoans ; 



Paramecium, 185 ; Vorticella, 189 ; Amoeba, 194. 

 Elytra : the hard wing-covers in beetles, 5. 

 Embryo : a young animal which is passing through its developmental 



stages, usually within the egg membranes or in the maternal uterus. 

 Encyst : the act of an animal in forming a cyst about itself. 

 Endopodite : the innermost of the two terminal branches of the typical 



crustacean foot ; crayfish or lobster, 32 ; sow-bug, 47 ; Daphnia, 56. 

 Endoskeleton : an internal supporting structure. • 

 Endostyle : a ciliated and glandular groove in the mid-ventral line of the 



pharynx in ascidians, 137. 

 Entoderm : the innermost layer of cells in the Cnidaria and Spongiaria ; 



Hydra, 160; tubularian, 165; campanularian, 171; sponges, 183. 

 Entosarc : the inner granular protoplasm in protozoans ; Paramecium, 185; 



Vorticella, 189 ; Amoeba, 194. 

 Epicranium : the sclerite forming the dorsal, median, and lateral walls of 



the head in insects, 12. 

 Epigynum : a cuticular plate covering or accompanying the female genital 



pore in many species of spiders, 26. 

 Epimeral plates : plates which may extend from the latero-ventral sides of 



the thorax in amphipods, 48. 

 Epiphragma : the disc of calcified slime with which a land snail can close 



the opening of its shell, 112. 

 Epipodite : a membranous projection of the protopodite ; crayfish or lobster, 



31 ; crab, 43. 

 Exopodite : the outermost of the two terminal branches of the typical 



crustacean foot ; crayfish or lobster, 32 ; sow-bug, 47 ; Daphnia, 56. 

 Extensor muscle : a muscle that extends an organ, 33. 

 Extremity : a paired lateral or ventral appendage of the body of an animal, 



used primarily for locomotion, although in many cases having second- 

 arily some other function, 1. 

 Exumbrella : the aboral side of a medusa, 167, 173, 175. 



Femur : the segment of an insect's or a spider's leg between the trochanter 

 and the tibia, 4, 12, 25. 



