696 GLOSSARY 



DimorpJiism. The condition in which a species exists in two distinct forms, 



as, for instance, male and female. 



Dioecious. Having the two sexes in two separate individuals. 

 Dissepiment. The partitions between the somites in annelids. 

 Distal. The position of a part of an organ away from the point of attachment 



opposed to proximal. 



Diverticulum. A sac-like projection of a tubular organ. 

 Dorsal. On or towards the back. 

 Dorsal lamina. A ciliated ridge in the mid-dorsal line of the pharynx in the 



ascidean. 



Ectocyst. The zooecium or outer wall of a bryozoan's body. 



Ectoderm. The outermost layer of cells in the Coelenterata. 



Ectosaro. The outermost layer of non-granular protoplasm in protozoans. 



Elytra. The imbricated scales on the back of certain annelids; the wing-covers 

 of beetles. 



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 leg. 



Endostyle. A ciliated, glandular groove in the midventral line of the pharynx 

 of tunicates and of Amphioxus. 



Entoderm. The innermost layer of cells in the Coelenterata. 



Entosarc. The interior granular protoplasm in protozoans. 



Ephippium. The shell in which the winter eggs of Cladocera are often con- 

 tained. 



Ephyra. A youthful stage in the growth of a scyphomedusan. 



Epigynum. A plate over the genital orifice in the female spider. 



Epiphragm. The disc of calcified slime with which a land pulmonate can close 

 the opening of its shell. 



Epipodium. A ridge along the side of the molluscan foot. 



Epistome. A projection above the mouth in certain bryozoans. 



Epitoke. The posterior sexual part of the body of certain annelids. 



Erineum. A pathological plant-growth caused by certain mites. 



Exopodite. The outermost of the two terminal branches of the typical crusta- 

 cean leg. 



Extensor muscle. A muscle that extends an organ. 



Extremity. A paired lateral or ventral appendage of the body of an animal, 

 used primarily for locomotion, although in many cases having secondarily 

 some other function. 



Exumbrella. The aboral side of a medusa. 



Fertilization. The union of the spermatozoon and the ovum. 



Flagellum. A vibratory thread-like projection of certain cells; the terminal 

 portion of the antennae in crustaceans. 



Flame cell* The terminal cell of an excretory tubule in the kidney of Plathel- 

 minthes. 



Flexor muscles. A muscle that bends an organ. 



Food vacuole. A globule of water containing food particles in protozoans. 



Frontal appendage. A pair of extra appendages between the second antennae 

 in certain Branchiopoda. 



Frontal organ. Sensory organs near the front end of certain nemerteans. 



Funiculus. A mesenteric strand connecting the stomach pouch with the body- 

 wall in bryozoans. 



Funnel. The siphon of a cephalopod. 



Furca. A pair of projections at the hinder end of the "body of copepods. 



