<§, 2T8. THE CRUSTACEA. 329 



beneath which is a pair of strong upper jaws {Mandibulae), which move 

 laterally by means of large muscles arising from the internal surface of the 

 cephalic and dorsal parts of the skeleton ; the internal border of these 

 jaws is hard and often denticulated. With the higher Crustacea, these 

 mandibles have a tactile organ [Palpus).'^'' Behind these mandibles are 

 two pairs of lower jaws [Maxillae), which are weaker, softer, and deficient in 

 palpi. They are composed of several pieces, except with the Myriapoda, 

 where they are fused into a kind of lower lip. Between the two mandi- 

 bles and the first pair of maxillae, there is a soft, tongue-shaped, and some- 

 times bifid process, which, also, may be regarded as an under-lip.**' 



With many of the lower Crustacea, the pai'ts about the mouth are vari- 

 ously modified, whereby they lose their peculiarities as masticatory organs. 

 Thus with the Poecilopoda, the mouth is simple, infundibuliform, and jaw- 

 less, — the mandibles and maxillae being changed into cheliform legs.'''' 



With the parasitic Crustacea, the organs of the mouth are changed into 

 parts for Suction. The two lips are prolonged into a kind of proboscis, 

 and the masticatory organs become more and more indistinct and finally 

 disappear entirely. This is best observed with the Caligina where the 

 mouth has the form of a beak pointing backwards, and the upper and lower 

 lips are joined together forming a long tube which contains the two very 

 long, horny, denticulated mandibles, while at its base are two palpiform, 

 rudimentary maxillae.'*^* With Argulus, the oral parts form a suctorial 

 apparatus even more complete. This is a very long proboscis, pointing 

 forwards, and out of which the two mandibles project in the form of two 

 small pointed stylets, while the maxillae are entirely wanting. *'' With the 

 Lernaeodea, and Penellina, on the other hand, the proboscis is short, and 

 contains two short mandibles, which are denticulated and hooked ; and on 

 its outside are two palpiform, rudimentary maxillae.*'^' But the oral parts 

 are most abortive with the Ergasilina and Bopyrina. Here, the upper and 

 under lips are blended together into a short proboscis without mandibles, 



3 With the Decapoda, Stomapoda, Amphipoda, 3 See Vander Uoeven, loc. cit. p. 16, PI. II. fig. 

 and the majority of Isopoda. With the Chilopoda, 1, A. (Limulus). 



these palpi exist only in a very rudimentary con- 6 Milne Edwards, Sur I'organisation de la 



dition ; and they are entirely wanting with Idothea, bouche chez les Crustaces suceurs, in the Ann. d. 



the Chilognatha, and the other lower Crustacea. Sc. Nat. XXVIII. 1833, p. 7S, PI. VIII. ; and espe- 



For the parts of the mouth of Crustacea, see the cially Burmeixter, in the Nov. Act. Nat. Cur. 



descriptions and figures contained in the works of XVII. p. 278, Tab. XXIII.-XXV. 



Savigny, Milne Edwards, and Erichson ; also ~ Jurine, loc. cit. p. 440, PI. XXVI. fig. 3-7, 



the various monographic works ujjon the Deca- 16 ; Vogt, loc. cit. p. 7, fig. 5.* 



poda, Isopoda, Myriapoda, Phyllopoda, Lophyro- 8 Nordmann, Microgr. Beitr. loc. cit. Taf. V.- 



poda, and Cirripedia, by 5wcA-o«), Brands, fiaiAAe, IX., and A'o^ter, loc. cit. Taf. IX. X. {Adheres, 



Treviranus, Zaddach, Jurine, Loven, Burmeis- Branchiella, Chondracanthus, Trackeliastes, 



ter, Martin St. Ans:e,kc. and Basanistes) ; also Burmeister, loc. cit. p. 



4 Astacus, Palaemon, Palinurus, Squilla. 310, Tab. XXIV. A. {Lernaeocera). 



* [ § 278, note 7.] According to Dana, the pro- fig. 2. b.). This last-mentioned author thinks that 

 boscls here mentioned is simply a spicula without the spicula in question is a poison weapon ; a view 

 any mouth-opening or mandibular appendages ; which is rendered probable from the fact that it has 

 the true mouth is posterior to this and has a trunk- glands connected with it, as in the stings of in- 

 form, with the buccal orifice on the under surface, sects, which glands have hitherto been considered 

 as in some genera of the Caligoidea, and provided salivary ; but they do not open into the mouth like 

 with regular mandibles ; see Amer. Jour, of Sc. ordinary salivary glands. Moreover, Leydig 

 1837, XXXI. p. 299, also Rep. on Crust, loc. cit. quotes the observation of Jurine that tadpoles 

 p. 1322. This has since been verified by Vogt pierced by this organ of Argulus, seemed poisoned 

 (Beitrage, &c., p. 7), and by Leydig (loc. cit. Sie- and soon died. — Ed. 

 bold and Kolliker's Zeitsch. U. p. 332, Taf. XIX. 



28* 



