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Show CRUSTACEA. Lin. Soc., II, 6; Encyclop. Method., Atl. d'Hist. Nat. CCCXXXVI 38-those appendages at·e only proper to the second, and four fol: ]owing feet( 1 ). NAUPREDIA, Lat. But ten feet, all in one continuous series; the base of the second and two following pairs provided with a vesicular body(2). CAPRELLA, L~m. Ten feet also, but in an interrupted series, commencing with th second segment, exclusive of the head; both this segment and th: following have two vesicular bodies~ and are totally deprived of feet(3). The other-OvALIA, Lat.-Lremodipoda have an oval body with tra~sversal segments. The stem of the antennre appears to be inarticulated, and the feet are short but slightly elongated; those of the second and third segments are imperfect and terminated b Io ng cy l'm e1 r i· ~a I J· O·i nt W•i thout a hook; their base is provided with Yana elongated vesicular body. They form the subgenus CvAMus, Lat.-Larunda, Leach. I have seen three species, all of which live on the Cetacea· It he m· ost comm.o n, Oniscus ceti ' L ·•' Pall ·' Spi.ci'l · Zool· F asc1·c .' X, Iv, 14; Squ'tlle de la Baleine, De Geer, Ins., VII vi 6· p . nogon. um cet~', F• a b· ; s av·ig ., Mem. sur les anim. s'a ns' ve'r tebyc., Fascic., I, v, 1, is also found on the Mackerel: it is called b fishermen Pou de Baleine. A second very analogous specie~ was brought to France by the late Delalande from the Cape of ?ood Hope. The third, which is much smaller, establishes Itself on the Cetacea of the Indian Ocean. ( 1) We should also refer to the L t . Dan., LVI, 1-3; Herbst., XXXVI ~r...:.~er~ the Sq~·t.lla .ventric?sa, Mull., Zoot. gener. He describes it as having ~x feet : t ~ncer lzne?rts, L., Is perhaps a con· ( 2) A subgenus fio d d , ' u oes not mclude the head. to me undescribed. un e on a species from th e coas t of France, wh1. ch appears (3) The Squilla lobata Mull zool D . batua, lb. CXIV 1o. th' 0 .. , · an., LVI, 4, 6; his Gammarus quadri/Q. ' • ~. e nzscus scolopendr 'de p 11 · 15, are Caprellre, but their s ecific diff, ot a, a ' Sptc. Zoo!. Fascic., IX, iv, had referred the Cancer line p . L erences are not well characterized. We pears doubtful. His Cance ft~ ., . t? the first, which, (see note one) now ap· Montag., Trans. Lin Soc rVII t O:":,t8 • Is probably a Caprella; the Cancer phatma, ' '' ' VI,~ IS a COngene fl' fi • • Method., Atl. d'Hist. Nat., cccxxivi r. ~s gure IS copied Encyc. and genus, see the Nouv. Diet. d'Hist '37. For details concerning this order the Crustacea. ·Nat., Ed. 11, and the work ofDesmareston ISOPOD A. 99 ORDER V. ISOPOD A( I). The Isopoda approach the Lremodipoda by the palpi of the mandibles being absent, but are removed from them in several other respects. The two anterior feet are not attached to the head, and belong, as well as the following ones, to a particular segment. They are always fourteen in number, unguiculated, and without any vesicular appendage at their base. The under part of the tail is furnished with very apparent appendages resembling leaflets or vesicular bursre, the two first or external of which, either partially or wholly, usually cover the others. The body is generally flattened, {1) The Polygonata, Fab., with the exception of the genus Monoculus. Messrs Audouin and Edwards-Ann. des Sc. Nat., Aout 1827, p. 379, 381-have published some interesting observations on the circulation of the lsopoda, and on that of the Ligire in particular. The heart resembles a long vessel extended above the dorsal surface of the intestine. From its anterior extremity arise three arteries, similar to those of the Decapoda. Lateral branches are also to be observed running from the heart towards the feet. On a level with the two fil'st segments ohhe abdomen (the tail), that organ receives, from the right and left, small canals (branchio-cardiac vessels) which seem to proceed from the branchia:. 'From their experiments on the Ligire, it 'Would appear that the venous system is less complete than in the Decapoda macroura, and that the blood driven fi·om the heart into various parts of the body, passes into lacuna: formed between the organs in the infe· rior part of the body which communicate freely with the ~;~.ff;erent vessels of the branchia:. The blood having traversed the respiratory apparatus, returns to the heart through the branchio-cardiac vessels. This disposition would form the tran· sition from the circulating system of the Decapoda to that of certain Branchio· poda. According to Cuvier, the two anomalous cords whi~h form the mediate portion of the nervous system of the Onisci-and, probably, of the other Isopoda and even of the Amphipoda-are not in complete juxtaposition, and may be distinguished throughout their whole course. There are nine ganglions without counting the brain, but the two first and two last are so closely approximated that we may reduce the number to seven. The second and six subsequent ones furnish nerves to the seven pairs of feet; the four anterior, although, by the order of the parts, analogous to the four last foot-jaws of the Decapoda, are true feet. The segments which immediately follow, or those which form the tail, receive their nerves from the last ganglion; these segments may be considered as simple divi· sions of one segment represented by this ganglion; thus we find that the number of these posterior segments varies. |