342 



THE CRUSTACEA. 



§286. 



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

 are iusei-ted 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 lanceohite branchial lamella, pointing forwards. 

 It is quickly distinguished 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-abdoniiual feet, which 

 act as gyratory organs. '^' 



4 With Phyllosoma, there is, at the base of t!ie 

 anterior feet, a small, ovoid, pedunculated append- 

 age, which may perhaps be regarded as a rudi- 

 mentary branchia ; see Milne Edwards, Hist. 

 Nat. d. Crust. II. p. 474, PI. XX VIII. fig. 15, a. 

 It is remarkable that, with another Stomapode 

 genus, Squilla, there are at the base of the ten 

 rapacious feet similar pedunculated appendages of 

 the form of oval lamellae (Milne Edwards, 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 rudimentary branchiae in the form of 

 simple vesicles or ramified processes {Milne Ed- 

 wards, loc. cit. II. p. 50Ü). With Caprella, and 

 Aegina, the first two posterior abdominal seg- 

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

 pyriform branchia ; while with Leptomera, there 

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

 six feet of the first three posterior abdominal seg- 

 ments ; see Müller, 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 

 Kröyer, 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. fig. 48—50 ; also Kröyer, 

 loc. cit. IV. p. 474, PI. V. fig. 70-76 ; and Roussel 

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

 to this last mentioned author, Cyamus ovalis 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 condition in order to be con- 

 vinced that they are special organs (Milne Ed- 

 wards, Ann. d. Sc. Nat. III. 1835, p. 329, PI. XIV. 

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

 inserted on the side of the feet of Leptomera. The 

 passage to 6V/ii(7/a,wliose branchiae are more highly 

 developed, is made by Cynthia. Each anal foot has 

 liere a bifurcated branchia, the two cylindrical 

 divisions of which are curved towards each other ; 

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

 402, PI. X. fig. 5. 



5 The delicate branchial lamellae usually assume 

 after death the form of vesicles, from being tilled 

 with blocxi, a phenomenon already mentioned (§ 285, 

 note 2). But, formerly, they were taken for special 

 organs whose function was unknown, and Bertkold 

 (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, 

 respiratory organs. 



These branchiae are easily perceived with Apiis 

 after death, and from tiie form which they then 

 assume, they have long been known as the prob- 

 lematical red sacs (ScAae^er, loc. cit. Tab. II. III. 

 VI. ; Zaddach, loc. cit. p. 14, Tab. II. fig. 13, B. 

 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, 

 Loschge (Naturforsch. Stück. XIX. p. 68, 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, Uas. Senckenb. 

 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. S, f. With Chirocephalus, Bran- 

 chipus, and Artemia, they have a more oval form 

 and exist on all the swimming feet. Rathk6 (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 (fViedemann\<t 

 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 respiratory organ, 

 since 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. 



Indeed, 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 

 branchiae, 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 incubatory 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,alsü Ibid. III. 1835, 

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



II. fig. 15, c, PI. .XX.X. fig. 1, 13, 16 (Gammarus 

 Phronima, yihilia, Hyperia); According to 

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



