212 



THE ACEPIIALA. 



<§>195. 



§ 195. 



It now remains to speak of a particular system of canals traversing in 

 all directions the body of the Lamellibranchia, which as yet has been 

 called the aquiferous system, because it is supposed to serve for an internal 

 respiration like that of the tracheae of insects.'" But, in the first place, 

 the existence itscH' of such a system has been denied, although there are 

 certain facts in its favor. 



When one of these animals is suddenly taken from the water, numerous 

 fine jets of water are seen to pass from these organs while the animal is 

 withdrawing its foot and the borders of the mantle within the shell. From 

 this fact it is evident that these orifices connect with aqueous reservoirs. 

 But these openings are very small and probably are closely contracted, for 

 they cannot be discovered either before or after the jetting out of the wa- 

 ter. <-> Orifices of this kind have as yet been found in a few species only ; 

 such are those in the extremity of the foot of Solen,^^'^ and that singular 

 tube found above the pedunculate anus of PmnaJ^^ 



The aquiferous canals themselves are not very apparent, being seen only 

 after injection. This last is easily performed by blowing through a small 

 tube inserted under the skin. There will then be seen a very beautiful net- 

 work of canals, which, nearly all of the same size, are spread out under 

 almost the whole skin and enter the interior of the body by larger canals. 

 These canals appear to be without walls, and have, in general, the aspect of 

 simple lacunae traversing the parenchyma of different parts of the body. 



13y some naturalists, this net-work of canals is regarded as a system of 

 lacunae circulating the blood ;'■'> but when they are inflated, another net- 



janus, Isis, 1819 ; Trcvirajriis, Beobacht. &c. p. 

 4i. and the beautiful figures of Pull, loo. cit.* 



1 Haer was the first to cull the attention to this 

 tquiferaus system with tlie Naiades {Froriep^s ueue 

 Nat. No. 265, 1826, p. a) after an analotjous one 

 had been pointed out with the Gasteropoda by 

 Delle Chiaje. Po/i, it is true, had recognized it 

 t)efure this, but he had taken them partly for trii- 

 cheae and partly for lymph oi blood-vessels. 



■i Meckel (Syst. d. vergleich. Anat. VI. p. 64) 

 went certainly too far when he affirmed that these 

 orifices are only accidental fissures. I have been 

 unable to find the orifices, which, accarding to Po/i 

 (loc. cit. Introductio, p. 42, 52), are upun the summit 

 of the cii'ri of the mantle and lead into a tracheal 

 system. 



u OriTiccs of this kind have been described and 

 figured by Delle Chiaje with So/en .lilifjua, as 

 Fori aqiiiferi (Descriz. &c. III. p. 60, Tav. XC. fig. 

 1'). These pores communicate jirobably with an 

 iquifernus system which Treciranns has seen in 

 the foot of Solen cnxis (Die Erschein. u. Gesetze 



des organisch. Lebens. I. p. 276). The orifice 

 which Garner has figured upon the middle of the 

 foot of Psammobia and Cardium, and to which 

 he has given the name of Porus pedalis, belongs 

 undoubtedly to this system ; see Trans, of the Zool. 

 Soc. II. PI. XVIII. fig. 2, 13, f. 



4 I have easily inflated the reticulated aquiferous 

 canals of this animal by this tube, which, iu Pinna 

 nobilis, sometimes protrudes far beyond the bor- 

 ders of the mantle, and which Poli (loc. cit. II. 

 p. 241, Tab. XXXVI. fig. 3, N. fig. 7, Z. and Tab. 

 XXXVII. fig. 1, S.) has figured as a Trachea. 



■'' See above § 192, note 11. The vascular net- 

 work which Poli (loc. cit. I. p. 8, Tab. IX.) has in- 

 jected with mercury in the mantle of a Unio, and 

 which he regarded as a lymphatic system, belongs 

 probably to the aquiferous system. T.'ie same in- 

 terpretation ought perhaps to be put \\\^on a san- 

 guineous net-work which he has figured in the man- 

 tle of a P/njirt (loc. cit. Tab. XXXVtll.). Delle Chi- 

 aje (Descriz. &c. III. Tav. LX.XV. f\-i. 6, Tav. 

 LXXVI. fig. 3, 6, and XC. fig. 1, 2, LXXXIX. fig. 



♦ [ § 194, note 20.] For full details on the bra'ich- 

 ial vessels of Teredo, and beautifully illustrated, 

 see Deshayes, loc. cit. p. 69, PI. VII. and Quatre- 

 fages, Meraoire, loc. cit. p. 67, PI. II. See also 

 IVilliams, On the Structure of the Branchiae and 

 Mechanism of Breathing in the Pholades and other 

 Ijimellibranchiate Mollusks, ia the Report of the 

 Brit. Assoc, for the Advancem. of Sc. for 1851, p. 82, 

 Uis first four conclusions are : 



'' 1. That the bloixl of all l<vmeUibranchiate mol- 

 lusca is richly corpusculated. 



" 2. That the branchiae in all species are com- 

 posed of straight parallel vessels returning upon 

 themselves. 



" 3. That the heart is systemic and not branchial. 



" 4. That the parallel vessels of the gills are 

 provided with vibratile cilia disposed in a linear se- 

 ries on either side of the branchial vessel, causinj 

 currents, wliich set in the direction of the current 

 of the blood iu the vessels." — Ed. 



