256 GLOSSARY 



Dioecious. Said of species in which the male and female gonads are in 



separate individuals. 

 Directive septa. Those placed opposite the siphonoglyphs of an actino- 



zoan. 

 Disk. In a starfish, the central portion from which the arms radiate. 

 Dissepiment. Septum. 

 Distal. Eemote from the point of origin or attachment. Converse of 



proximal. 

 Diverticulum. An outpocketing from a tube, a caecum. 

 Dorsal. Pertaining to the back. 

 Dorsal lamina. A ciliated ridge on the dorsal side of the pharynx of 



an ascidian. 

 Dorsoventrally. From the dorsal to the ventral position. 



Ectoderm. The outer embryonic or germ layer. 



Ectoparasite. A parasite on the outside of the body. 



Ectoplasm. Outer protoplasmic layer of a protozoan. 



Efferent. Carrying away, as a vessel which leads away from an organ. 



Elytra. The modified forewings of a beetle; the scales of a scale- 

 worm. 



Embryo. An immature organism. 



Encyst. To enclose in a cyst. 



Endoderm. The inner embryonic or germ layer. 



Endoparasite. A parasite inside the body. 



Endophragmal skeleton. Chitinous plates which cover the nerve chain 

 and ventral blood sinus in the thorax of certain crustaceans. 



Endoplasm. Inner protoplasmic portion of a protozoan. 



Endopod. In a biramous appendage of an arthropod, the branch which 

 is nearer the midline of the body. 



Endoskeleton. An internal skeleton. 



Endostyle. A ciliated groove in the ventral wall of the pharynx of 

 certain primitive chordates. . 



Ephyra. The stage which follows the scyphistoma in the development 

 of a scyphomedusan. It consists of a disklike body with 8 marginal 

 notched lobes. 



Epicardium. A hollow process from the pharynx of some ascidians. 



Epipharynx. In some insects, a projection from the roof of the mouth. 



Epiphysis. A plate joined to the base of the alveolus in the mouth 

 parts of an echinoid. 



Epipod. A membranous projection from the basipod of certain crus- 

 tacean appendages. It extends into the gill chamber. 



Episternum. Among invertebrates, a lateral piece next to the sternum, 

 as in arthropods. 



