$197. 



THE ACEPHALA. 215 



These nuclei are very solid and ought to be regarded as the secreting 

 bodies. They are sometimes so large as to be visible to the naked eye as 

 inorganic concretions, and, as they contain uric acid, they may well be 

 compared to renal calculi. '"> The walls of these kidneys are surrounded 

 by a distinct net-work which arises from the large venous reservoir in 

 which the afferent blood of the body is accumulated. A small portion of 

 the blood which circulates in the kidneys passes directly to the heart ; but 

 the rest is emptied into the pulmonary arteries.'^^ 



CHAPTER IX 



ORGANS OF GENERATION. 



§ 197. 



The Acephala throughout, propagate by genital organs. With the 

 Tunicata only, is there also observed multiplication by gemmation. 



This occurs with the compound and some of the simple Ascidiae, which 

 remind one of the Zoophytes and more particularly the Polyps, which they 

 resemble from other conditions of the organization. The buds are always 

 developed at the lower extremity of the body, appearing first as small pyri- 

 form projections, covered by the general envelope of the mantle, into which 

 the circulation is prolonged. 



Gradually, an Ascidian is developed upon the round summit of this pro- 

 jection, while its peduncle is lengthened and somewhat constricted ; this 

 continues until the body of the new individual is entirely separated from 



5 Similar concretions had already been seen and aside from the fact of their containing uric acid 



described with several of the Lamellibranchia by (Garner, Trans, of the Zool. Soc. loc. cit. p. 92, and 



Poll, who has regarded the kidneys as organs for Owen, Lect. on Comp. Anat. &c. p. 284), a point 



the secretion of the lime of the shell' ; see his classic upon which I was not before satisfied, 



work, Introductio, p. 18, also Tom. II. p. 86, The chemical composition of these concretions, 



Tab. XX. fig. 4, 6, k, fig. 12, 13 {Cytherea chio), however, satisfies me that these organs are truly 



p. 143, Tab. XXVI. fig. 11, 12, 13, y. {Pectun- kidneys. 



cuius pilosus), and p. 241, Tab. XXXVII. fig. 5, 6 This is the mode of circulation of the blood 



6, 3, D {Pinna nobilis). through the kidneys,according to Bojanua, loc. cit. 



These concretions were irregular and of a red or But the opinion of Treviratius is different. Ac- 

 yellow color. I have recently found, in several in- cording to liim all the blood returning from the 

 dividuals of Pectunculus pilosus, amber-colored branchiae traverses the glands of Bojanus before 

 concretions, mostly round, of variable size, giving reaching the heart (Beobacht. aus. d. Zoot. &c. p. 

 these two organs the appearance of a fish's ovary 49). As these organs are not easily found, it will 

 filled with eggs. Having collected a considerable be difficult to determine this point positively by 

 quantity of these concretions, I sent a part of them direct observation. It is only by following analogy 

 to Herrn Von Babo of this city, who has favored that Bojanus^ opinion can be probable in its essen- 

 me with their qualitive analysis. The result was tial point, — which is, that if the glands of Bojanus 

 that those with a conchoidal fracture were com- are the analogues of the venous appendages of the 

 posed principally of phosphate of lime with a trace Cephalopoda, and of which I am persuaded with 

 of magnesian phosjihate, and a small quantity of Van der Hoeven (MeckePs Arch. 1S2S, p. 502) is 

 organic matter which behaved with nitric acid ex- the case, then they connect with the veins which 

 actly Uke uric acid. Notwithstanding Bojawus go to the branchiae, and not with the arteries which 

 <Isis, 1S19, p. 46, 1820, p. 404) has taken much go from the branchiae to the heart, 

 pams to prove that these organs are pulmonary, The blood-current in the glands of Bojanus, 

 yet the view that they are kidneys has found most therefore, ought to pass towards the branchiae and 

 support (Treviranus, in Tiedernayin^s Zeitsch. f. not towards the heart. 

 fii/s. I. p. 53, and Car us, Zoot. 1834, U. p. 650), 



