$ 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 
described with several of the Lamellibranchia by 
Poli, who has regarded the kidneys as organs for 
the secretion of the lime of the shell ; see his classic 
work, Introductio, p. 18, also Tom. II. p. 86, 
Tab, XX. fig. 4, 6, k, fig. 12, 18 (Cytherea chio), 
p. 148, Tab. XXVI. fig. 11, 12, 13, y. (Pectun- 
culus pilosus), and p. 241, Tab. XX XVII. fig. 5, 
6, 3, D (Pinna nobilis). 
These concretions were irregular and of a red or 
yellow color. I have recently found, in several in- 
dividuals of Pectunculus pilosus, amber-colored 
concretions, mostly round, of variable size, giving 
these two organs the appearance of a fish’s ovary 
filled with eggs. Waving collected a considerable 
quantity of these concretions, I sent a part of them 
to Herrn Von Babo of this city, who has favored 
me with their qualitive analysis. The result was 
that those with a conchoidal fracture were com- 
posed principally of phosphate of lime with a trace 
of magnesian phosphate, and a small quantity of 
organic matter which behaved with nitric acid ex- 
actly like uric acid. Notwith ding Bojanus 
aside from the fact of their containing uric acid 
(Garner, Trans. of the Zool. Soc. loc. cit. p. 92, and 
Owen, Lect. on Comp. Anat. &c. p. 284), a point 
upon which I was not before satisfied. 
The chemical composition of these concretions, 
however, satisfies me that these organs are truly 
kidneys. 
6 This ig the mode of circulation of the blood 
through the kidneys,according to Bojanus, loc. cit. 
But the opinion of Treviranus is different. Ac- 
cording to him all the blood returning from the 
branchiae traverses the glands of Bojanus before 
reaching the heart (Beobacht. aus. d. Zoot. &. p. 
49). As these organs are not easily found, it will 
be difficult to determine this point positively by 
direct observation. It is only by following analogy 
that Bojanus’ opinion can be probable in its essen- 
tial point, — which is, that if the glands of Bojanus 
are the analogues of the venous appendages of the 
Cephalopoda, and of which I am persuaded with 
Van der Hoeven (Meckel’s Arch. 1828, p. 502) is 
the case, then they connect with the veins which 
go tothe branchiae, and not with the arteries which 
Asis, 1819, p. 46, 1820, p. 404) has taken much 
pains to prove that these organs are pulmonary, 
yet the view that they are kidneys has found most 
support (T'reviranus, in Tiedemann’s Zeitsch. f. 
Phys. I. p. 53, and Carus, Zoot. 1834, Il. p. 650), 
go from the branchiae to the heart. 
The blood-current in the glands of Bojanus, 
therefore, ought to pass towards the branchiae and 
not towards the heart. 
