14 Prof. J. C. Scliiodte on the Structure of 



is turned pei-pendicularly 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 niaxillipeds 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 tiibe 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 maxillae. 



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, sejDarating itself from the stem by a 

 short neck, in which tliere 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 maxillge; 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 {^ga)j or of 

 a thin, triangular, pointed knife-blade {CymotJioa) . 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 maxillae. 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 maxillaj 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 u:Ega and Cy- 

 mothoa will serve to place this account in a clearer light. 



12. When the mouth of ^^ga is examined from beneath, 



