342 



THE CRUSTACEA. 



§286. 



ary appendages, which hang freely from the base of some of the feet, or 

 are inserted isolatedly on the sides of the body.''*' 



4. The Phyllopoda have, at the base of each of their numerous swim- 

 ming feet, an ovoid or lanceolate branchial lamella, pointing forwards. 

 It is quickly di.;tinguished by its thin, glabrous covering, in opposition to 

 that of the other divisions of feet, which are bristled. <'"> 



5. With the Amphipoda, the rapacious and ambulatory feet, excepting the 

 first and last pairs, are those only which are provided with respiratory organs. 

 These last consist of oval or round glabrous lamellae, situated internally at 

 the base of the five middle feet. They receive, constantly, fresh water by 

 the movements of the three anterior pairs of post-abdominal feet, which 

 act as gyratory organs. '^' 



< With Phyllosoma, there is, at the bas<; of thu 

 anterior feet, a small, ovoid, peiiuiiculated append- 

 age, which may i)erhaps be regarded as a rudi- 

 mentary branciiia ; see Milne Kdwards, llist. 

 Nat. d. Crust. II. p. 474, PI. X.YVIII. ti-. 15, a. 

 It is remarkable that, with another Stjmapode 

 genus, Hr/ui/lti, there are at the base of the ten 

 rapacious feet similar pedunculated appendages of 

 the form of oval lamellae {Milne Edioards, Hist. 

 Nat, d. Crust. II. p. 512, PI. XXVI. fig. 15, PI. 

 XXVII. fig. 13, 14, b.). These, also, would be re- 

 garded as rudimentary branchiae, did not these 

 Crustacea have distinct branchial organs (see 

 below). With Alima, the oval feet have some- 

 times very rudunentary branchiae in the form of 

 simple vesicles or ramified processes (Milne Ed- 

 wards, loc. cit. II. p. 506). With Caprella, and 

 Aegina, the first two posterior ftbdominal seg- 

 ments have, upon the sides, a simple, very soft, 

 pyriform branchia ; while with Leptomera, there 

 is a vesicle of the same nature at the base of the 

 six feet of the first three posterior abdominal seg- 

 ments ; see Muller, Zool. Uanic. Tab. LVI. fig. 5, 

 and Tab. CI. fig. 2 ; Templeton, Transact, of the 

 Entomol. Soc. I. p. 193, PI. XXI. fig. 7, f. ; and 

 Krbyer, Naturhist. Tidskr. IV. p. 490, PI. VI.- 

 VIII. With Cyamus, the respiratory organs are 

 even more developed. They consist of four long, 

 simple cylinders inserted on the sides of the first 

 two posterior abdominal segments, and projecting 

 over the back ; see Treviranus, Verm. Schrift. II. 

 p. 9, Taf. I. fig. 1-3, and Beobacht. aus. d. Zoot. u. 

 Physiol, p. 32, Taf. VII. ftg. 4S— 50 ; also Kriiyer, 

 loc. cit. IV. p. 474, PI. V. fig. 70-70 ; and Roussel 

 de Vauzime, loc. cit. p. 248, PI. VIII. ; according 

 to this last mentioned author, Cyamus oua/is has 

 four double, branchial cylinders. These branchiae 

 of Cyamus have often been taken for metamor- 

 phosed feet, but it is only necessary to examine 

 them in their earliest cou(lition in order to be con- 

 vinced that they are special organs (Milne Ed- 

 wards, Ann. d. Sc. Nat. III. 1S35, p. 329, PI. XIV. 

 fig. 14). At this epoch they are as pyriform as those 

 Inserted on the siile of the feet of Leptomera. The 

 passage to Squilla,\\'hi>se branchiae are more highly 

 developed, is made by Cynthia. Each anal foot has 

 here a bifurcated branchia, the two cylindrical 

 divisions of which arc cui-ved towards each other ; 

 see Milne Edwards, Hist. Nat. d. Crust. H. p. 

 462, PI. X. fig. 5. 



5 The delicate branchial lamellae usually assume 

 after death the form of vesicles, from being filled 

 with blood, a phenomeuon already mentioned (§ 2S5, 

 note 2). i$ut, formerly, they we-e taken for special 

 organs whose function was unknown, and Berthold 

 (Isis, 1830, p. 693) has regarded those of Apus as 

 male genital organs -, while the remaining pilose 

 divisions of swimming feet were, according to him, 

 rospiratory organs. 



These branchiae are easily perceivc-d with Apux 

 after death, and from the form which they then 

 assume, they have long been known as the prob- 

 lematical red sacs (6'cAae^er, loc. cit. Tab. il. III. 

 VI. ; Zaddacli, loc. cit. p. 14, Tab. II. fig. 13, U. 

 Tab. XIV.). In 1830 (Isis, p. 429) I gave the cor- 

 rect interpretation of these organs which, like the 

 swimming feet of these animals, diminish in size 

 from before backwards ; but, already, before me, 

 Losckge (Naturforsch. Stuck. XIX. p. 63, Taf. III. 

 fig. 6, 7, 10) had recognized their nature. With 

 Limnadia, and Isaura, the branchiae are very 

 ' long and of a brown-red color, but are wanting on 

 the last swimming feet ; see Brongniart, loc. cit. 

 p. 86, PI. XIII. fig. 7, 8 ; Straus, Mus. Senckeub. 

 loc. cit. p. 124, Taf. VII. fig. 13, 14, r., 15, k. ; 

 Joly, loc. cit. p. 299, PI. VII. fig. 2, 6, 7, f. and 

 PI. VIII. fig. 8, f. With Chirocephalus, Bran- 

 chipus, and Artemia, they have a more oval form 

 and e.>kist on all the swimming feet. Rathki (Zur 

 Fauna der Krym. p. 108, Taf. VI. fig. 14, 19-21), 

 has figured, probably from dead individuals, those 

 of Artemia as vesicular bodies. In the figures of 

 Jurine (Hist. d. Monocl. PI. XXI. XXII.), made 

 for the memoir oiPrivost, the branchiae of Chiro- 

 cephalus are not seen at first, but with a little at- 

 tention may be discovered. Gaede {iViedcmann'.'i 

 zool. Magaz. I. p. 88), Berthold (Isis, 1830, p. 689, 

 Taf. VII. fig. 1), and Zaddach (loc. cit. p. 11, Tab. 



I. fig. 17, Tab. II. fig. 10) have regarded the large 

 dorsal shield of Apus as a respiratoi-y organ, 

 smce its lateral halves are traversed by blood-cur- 

 rents running close to each other (Schaeffer, loc. 

 cit. p. 72, Tab. I. fig. 5, b. b.), and thence passing 

 directly towards the anterior extremity of the 

 heart. 



Bideed, from the vascularity and delicateness of 

 the under surface of this shield, one would be quite 

 disposed to attribute to these parts a participation 

 in the respiratory act. 



t' For a long time, the multi-articulated, bristly, 

 anal feet of these small Crustacea were regarded as 

 brauchiae, for the true branchiae are quite concealed 

 under the internal surface of the anterior feet. 

 Even after the attention had been directed to these 

 organs, their form was often misapprehended ; for 

 when these animals are a long time dying, their 

 branchiae are changed, from congestion, into ampul- 

 lae. With the Amphipoda, it is easy to distinguish 

 the branchial lamellae from the uicubatory lamellae 

 at their side, for the borders of these last are bris- 

 tled ; see Straus, loc. cit. p. 57, PI. IV. fig. 10, 11, 

 h. (Hiella) ; Zenker, loc. cit. p. 8 (Gammarus) ; 

 Milne Edwards, Ann. d. Sc. Nat. XX. 1830, p. 

 357, PI. X. fig. 7, PI. XI. fig. l,also Ibid. III. 1835, 

 PI. XIV. fig. 9, and Hist. d. Crust. III. p. 6, PI. 



II. fig. 15, c, PI. XXX. fig. 1, 13, 16 (^Gammarus 

 Fhronima, yibilia, HyperiaX According to 

 Savigny''s figure (Uescrip. de I'Egypte, loc. cit. PI. 



