A COMPLEX STRUCTURE. 219 



of protopodite, exopodite, endopodite, and the like; but 

 the epipodite (or inner branch) of the first pair of max- 

 illae is rudimentary, while that of the second pair is 

 large and shaped like a spoon. It is termed the " scap- 

 hognathite," and its function is to "cause a current of 

 water to traverse the gill-chamber by constantly bailing 

 water out of it." 



To the next segment are appended the biting jaws, or 

 " mandibles," each consisting of a large protopodite, and a 

 small endopodite, termed the "palp" (or organ of touch), 

 the exopodite remaining undeveloped. 



The aperture of the mouth is situated between the 

 bases of the mandibles, bounded behind by a forked pro- 

 cess, called the " labium," or " metastoma," and in front 

 by a single plate, the " labrum," or upper lip. 



The next segment sustains the long antennae, or feelers, 

 each consisting of a short protopodite, and a long, jointed, 

 and segmented endopodite, with an exopodite which is 

 little more than rudimentary. 



In front of the great antennae we find the " anten- 

 nules," or smaller antennae, each composed of a protopo- 

 dite and a segmented endopodite and exopodite, which 

 are nearly of equal size. Finally, attached to the first 

 segment of the head are the eyes, each borne upon an eye- 

 stalk formed by the protopodite. The gill-chamber con- 

 sists of a great prolongation downwards of the " pluera " 

 of the thoracic segments, and the gills are attached to 

 the bases of the legs. 



Such is the complex structure of the Common Lobster,* 

 .which may fairly be regarded as a type of the higher 

 Crustacea. 



* Nicholson, "Manual of Zoology," pp. 205, 206. 



