30 
DE. a. EOLLESTON AND IVIE. C. EOBEETSON ON THE AQIJIEEEOIJS 
M. LlYCAZe Duthiers has discovered and described* yet another route than that of 
the organ of Bojanus, by which, in the Dentalium and Pleurobranchus^ water from with- 
out can find its Avay into the interior of vessels carrying blood, and carrying it in these 
instances towards the heart, and not towards the gills. 
GEGENBAURf differs from these authors merely in postulating the existence of orifices 
of exit as well as of entrance for the water ; and these he holds to correspond with the 
puncta scattered over the foot-surface, and visible in great abundance occasionally along 
and near its free edge. 
Voi^ KengartenJ exactly reverses the functions thus supposed to belong to the punc- 
tated foot-pores, and the passage through the organ of Bojajstus severally. 
In a paper read by us§ before the Royal Society, February 3, 1859, we spoke of the 
water-vascular system as liaAing its outlet in close approximation to the external orifice 
of the organ of Bojanus ; and its inlet we suggested might be indicated by the position 
of the parasites which are not rarely to be seen studding the foot-surface and marking 
out the presence of its numerous pores. Gegenbaur, we observe ||, considers that the 
great liability of the foot to injury from the entrance of foreign bodies into these pores, 
is an argument for regarding them as exhalant rather than inhalant orifices. 
Further investigations, carried on by us subsequently to the reading of that paper, 
showed us that our "views as to the oviducal system in the Lamellibranchiata were 
founded in error. An exceedingly courteous notice of this mistake by M. Lacaze Du- 
THiERS^ in the ‘Proceedings of the Royal Society,’ rendered an earlier retractation of 
this part of our paper unnecessary. Our views, on the other hand, as to the permeation 
of the bodies of the Lamellibranchiata by a system of vessels distinct from those in 
which the blood is contained, remain much what they were. 
Before stating our views, and the arguments by which we would support them, we 
would say that the “ permsceral chamber ” of the Brachiopoda, as described by Mr. Han- 
cock** in a paper in the ‘ Philosophical Transactions,’ which was published subsequently 
to the reading of our paper already referred to, holds much the same relation to the 
circulatory and reproductive and other viscera, as the system which we have called 
“ aquiferous ” in the Lamellibranchiata. As Mr. Hancock ff has himself pointed out 
the close correspondences of the two systems, we will but remark upon one point of dis- 
crepancy between them. In the Brachiopods the genitalia are packed into the main 
stems of the arborescent perivisceral system, in the direct course of the stream, if we 
may speak of it as a water-vascular system ; in the Lamellibranchiata, or, at all events, in 
the family Unionidse, the cseca of the generative gland are appended laterally to the 
* Aim. des Sciences Naturelles, tom. xi. 1859, p. 255 ; tom. vu. Proceedings of the Eoyal Society, vol. x. 
p. 194. 
t Gnmdxuge der vergleichenden Anatomie, p. 352, 1859. 
it Diss. Inaug. Dorpat, 1853, cit. Vox Hesslixg, loc. cit. p. 236. 
§ Proceedings of the Eoyal Society, vol. ix. no. 34. p. 634. Eebroary 3, 1859. 
11 Loc. cit. p. 352. ^ Proceedings of the Eoyal Society, vol. x. no, 37. p. 193. 
** Philosophical Transactions for 1858. Eead May 14, 1857. tt Loc. cit. p. 844. 
