AKD OVIDUCAL SYSTEM IN THE LAMELLIBEANCHIATE MOLLIJSKS. 
33 
vessels we have* never succeeded in filling the pericardium from the blood-vessels, easy 
though it be, as in Experiment 1, to make the injected fluid take the reverse direction, 
more direct evidence is yet needed in support of our view of the organ of Bojanus as 
the channel for an inwardly-setting current of water. The following considerations 
seem to us to show conclusively that, though Experiment 1 shows that it is possible for 
intrapericardial fluid to find its way outwards through the renal organ, such is not the 
direction usually taken by the fluid contained in the complex aquiferous system thus 
constituted. 
1st. If we examine with the microscope the fluid contained in the pericardial space, 
we shall find it to contain, besides the morphological elements of blood, certain foreign 
bodies, such as the Aspidogoster conchicola and infusoria. Now these creatures must be 
supposed to have found their way inwards through the organ of Bojanus. 
2ndly. The external orifice of the organ of BoJAifUS may be seen in a living Anodon 
(and, from its lying exposed in the gill-cavity, with yet greater ease in a JJnio margariti- 
ferra) to execute movements of alternate opening and shutting, similar in character to 
those executed, as has been repeatedly noticed, by the analogous organ in the Ptero- 
poda. These movements are repeated as frequently as once in every ten seconds (or 
oftener) in the TJnio margaritifera ; and they possess, there can be little doubt, in these 
as in other moUusks, the power of filling with water the cavities into which they lead. 
3rdly. The glandular portion of the compound organ of Bojanxjs has its opening into 
the pericardium guarded by a funnel-shaped projection which acts as a valve looking 
heartwards, and offers resistance consequently to fluid passing outwards from that lacuna. 
4thly (Experiment 3). Fluid thrown in by the external orifice of the organ of Bojanus, 
as it is either artificially, as in the Anodon., or naturally, as in the JJnio margaritifera, 
exposed in the gill-ca\ity, finds it way even more easily into the pericardium than fluid 
thrown, as already described, into the pericardium finds its way into the gill-cavity by 
the reverse route. This experiment is but an imitation of what we may suppose to take 
place whensoever the animal by opening its valves dilates its pericardial space. As an 
immediate consequence of this dilatation, water is ingested into the blood-vascular 
system, and is forthwith applied to the purpose of distending the foot and protruding it 
through the opening valves. 
Up to this point our views are in accordance with those adopted by several authors, 
though we are not aware that our method of proof has been employed by any other 
observers, so far as its detailed application is concerned. 
^ye will now proceed to give our reasons for supposing that another system of tubes 
comes in aid of the blood-vascular system, and receives from it the fluid which that 
system has been the means of taking up in the manner described. Our arguments will 
go to show that water is transferred from the blood-vessels in the foot of the freshwater 
* M. Laitgee’s language (Denkacliriften d. Akad. Wiss. loc. cit. p. 43), in describing bis success in such 
injections, is so qualified, “ und sab docTi nicht immerj as to allow one, without discourtesy, to give less 
weight to his views on this than on most other points. 
MDCCCLXII. F 
