L obster — A ppen dages , A natomy. 
17 
with its gnathobase, and a small “palp” of three segments Wall- 
representing the rest of the protopodite with the endopodite. NosT] 
The rest of the appendages may be briefly disposed of. The 
walking-legs (Fig. 1) can easily be seen to correspond, segment for 
segment, with the third maxillipeds, except that they have no 
exopodites. The large claws ( chelipeds ), like the two pairs of legs 
immediately succeeding them, are chelate or pincer-like. This 
modification, which is very frequent among Crustacea in limbs 
used for seizing food, is brought about- by the penultimate segment 
of the limb growing out into a process, the “ immovable finger,” 
lying alongside the last segment, which can be brought into con- 
tact with it and is known as the “ movable finger.” 
The movable stalks, upon which the eyes are set, are divided 
into two segments and in a few Crustacea they are even composed 
of three. The view was long and widely held that these stalks 
were the equivalent of a pair of appendages like the legs or jaws. 
There are some reasons, however, for believing that this is not the 
case, and the eye-stalks are therefore omitted from the list of 
the Lobster’s appendages given here. 
Some of the gills ( branchiae ) of the Lobster are seen attached 
to the epipodites of the thoracic limbs. Their exact arrangement, 
however, is more clearly shown by the preparations in spirit 
exhibited alongside. In a transverse section through the thorax 
it is seen that the gill attached to the epipodite of the leg lies on 
the outer side of the branchial chamber. It is known as a 
“ podobranchia.” Next to it on the inner side are two gills which 
spring not from the leg itself, but from the membrane of the joint 
between the leg and the body. These are called “ arthrobranchiae.” 
Finally, next the inner wall of the chamber, is a gill attached to the 
wall of the body itself and known as a “ pleurobranchia.” The 
complete set of four gills is not present on every thoracic somite 
and the arrangement differs very much in different Crustacea. 
Internal Anatomy.— The general arrangement of the internal 
organs of the Lobster is shown by a preparation in which the 
animal is dissected from the side (Fig. 4). The alimentary canal 
begins with a short gullet or “ oesophagus ” leading upwards from 
the mouth into the large “ stomach,” from which the “intestine ” 
runs straight backwards to the vent on the under side of the 
telson. The stomach is not very suitably named, for it is probably 
not the place where the chief processes of digestion go on, but on 
the other hand it contains a complex apparatus known as the 
“ gastric mill ” which acts as a gizzard in grinding up the food. 
c 
