398 The Lobster ; Its Structure and History. [July; 
ing of little lamellæ fastened together, forming a gill. These gills 
are packed away under the carapace. There are twenty on each 
side. The fifth limb bears one. In the fourth we find still an- 
other organ, a thin leathery structure with scattered hairs, the 
epipodite, the function of which is to keep the gills apart. This 
limb bears four gills, as do the third and second. In the second 
and third limbs the inner distal angle of the next to the last joint 
is greatly elongated, forming with the last joint a pincer or 
chela; limbs thus formed are said to be chelate. The first pair 
of thoracic limbs are greatly enlarged, and it is the outer instead 
of the inner angle of the joint next to the last which is elongated 
to form the pincer. It bears three gills. 
We now come to the appendages of the head, and among 
them we again find the exopodite. The six posterior pairs are 
commonly called the “mouth parts.” We first find, in going 
forward, three pairs of mavzillipeds, each composed of a protopo- 
dite, exopodite, and endopodite. The outer pair are larger than 
the others, the basal joints are hard and toothed like a saw; they 
bear each three gills. The second pair bear one small gill and 
the third are gilless. In front of the. maxillipeds are the two 
pairs of maxilla. They are delicate, almost membranous. The 
epipodite of the posterior one, called scaphognathite, is in life in 
constant motion, baling out water from the gill cavity, thus 
creating a current over the gills and aiding in respiration. W® 
next come to the mandibles, a pair of hard protopodites with 
cutting edges, and a delicate three-jointed endopodite termed a 
palpus. Between the mandibles is the mouth. It is pounded 
behind by a bifurcated process, the metastoma, and in front by a 
simple enlargement, the labrum. In front of the mouth the 
sternal surface bends abruptly upward. Above this flexure we 
find the larger antennæ, which consist of a protopodite and en- 
dopodite, the exopodite being represented by a small spine. Still 
farther in advance are the smaller antennæ, called the anten- 
nulæ. This finishes the number of segments. Reviewing, we 8° 
that we have eight cephalic, five thoracic, and seven abdominal. 
It will be seen that the writer does not recognize any segment 
corresponding to the eyes, and that he believes the telson to bee 
somite. The reasons for the former are chiefly embryological 
for the latter, the fact that the intestine passes through it, eg 
gether with certain reasons derived from the development of the 
young lobster. The mere absence of appendages has no great 
weight 
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