14 Prof. J. C. Schiodte on the Structure of 
is turned perpendicularly downwards and on the sides joins the 
maxillary lobes of the second pair, which also are converted 
into a semicylindrical duct, and of which the ends are expanded 
into a sort of lip; the palpi of the maxillipeds sometimes 
also enter into the combination. Thus a short soft tube is 
produced, which, by means of fringes, warts, and small hooks 
round the aperture, is specially adapted for closing tightly 
against a surface. Inside this tube we find foremost a pair of 
instruments designed for stinging, clipping, cutting, gnawing, 
or scratching, and which are the transformed mandibles; and 
behind them, again, a pair of fine saws or rasps are seen, by 
means of which the wound made by the mandibles may be 
further extended, lacerated, or deepened; this second set of 
instruments is formed by the first pair of maxille. 
As regards the mandibles, the conversion is effected in the 
following way :—the stem is elongated, its sliding articulation 
at the base disappears, and it becomes almost immoveable ; the 
inner lobe disappears entirely ; the outer lobe is twisted abruptly 
downwards and forwards, separating itself from the stem by a 
short neck, in which there is an imperfect membranaceous arti- 
culation, and penetrates at once, just at the bend, into the inte- 
rior of the sucking-tube, slipping in from the side between the 
labrum and the expanded ends of the second pair of maxille; the 
lower part of this lobe, which consequently is inside the suck- 
ing-tube, assumes the shape either of a triangular, pointed, at 
the apex sharp and hooked scratching-instrument (4/ga), or of 
a thin, triangular, pointed knife-blade (Cymothoa). Although 
the stem of the mandible, on account of its limited mobility, 
only requires small space for its own muscles, it never- 
theless retains a considerable size, as it must accommodate not 
only the muscles of the palpus, but also those of the moveable 
lobe, of which, however, the muscles also combine with those 
belonging to the second pair of maxille. Upon the whole, it 
may be observed that the masticating muscles of Crustacea 
are, as is also the case in fishes, combined and coalescent with 
each other to that degree that it becomes difficult to distin- 
guish between their different portions, and all the organs of 
the mouth are really moved collectively to a certain extent. 
The maxille of the first pair are reduced to slender stiff 
stylets, surrounded and hidden by those of the second pair, 
of which the lobes in front meet in the middle; the stylet is 
formed by the stem and the moveable middle lobe, which on 
the apex carries a number of pointed hooked thorns. : 
A more detailed description of the mouth in 4%ga and Cy- 
mothoa will serve to place this account in a clearer light. 
12. When the mouth of Aga is examined from beneath, 
