598 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
capillari vitreo, vense alicui intruso, globulos opacos vere orbiculares baud paucos 
videbis ; ac sanguineos nostros globulos magnitudine pluriniura excedentes. Hi vero 
globuli ut prse sanguinis globulis pauci sunt, ita aqua quaedam limpida innatant, et 
paulatim prse gravitate ad unuin syphonem descendant. Idem quoque experimentum 
de succo vitali in cochleis fluviatilibus feci ; idemque coagulum sub-cseruleum, igni 
admotus, dedit.” Iron and manganese have been detected by Erman in the blood 
of Helix Pomatia and Planorbis corneiis. 
To the historical references formerly given, it must be added that, more recently, 
two elaborate memoirs, “On the Blood-corpuscle considered in its different Phases of 
Development in the Animal Series,” have been published in the Philosophical Trans- 
actions (1846), of which one relates exclusively to the blood of invertebrate animals. 
Emanating from a physiologist so distinguished as Mr. T. Wharton Jones, these 
memoirs are entitled to the highest consideration. Although confined “to the more 
readily procurable examples of the divisions Annulosa and Mollusca,” those on the 
Crustacea and Insects excepted, in no instance have I been able to verify the observa- 
tions of this author. 
In their most recent communication to the Royal Society*, Alder and Hancock 
adduce additional facts corroborative of their former conclusions. They maintain 
“ that in the Mollusks there is a triple circulation : first, the systemic, in which the 
blood propelled along the arteries to the viscera and foot is returned, with the ex- 
ception of that from the liver-mass, to the heart through the skin ; there it becomes 
partially aerated, the skin being provided with vibratile cilia, and otherwise adapted 
as an instrument of respiration ; second, the portal, in which venous blood fron» 
the system is driven by a special heart to the renal and hepatic organs, and probably 
to the ovarium, where it escapes, doubly venous, with the rest of the blood which 
has been supplied to these organs from the aorta, and which is therefore only singly 
venous, to the branchiae ; third, the branchial circulation, in which flows only the 
more deteriorated blood brought by the hepatic vein, but in which also that blood 
undergoes the highest degree of purification capable of being effected in the economy, 
namely, in the special organ of respiration. This triple circulation has not yet, as 
far as the authors are aware, been described in the Molluscan Sub-kingdom. Since 
the blood in Doris is returned to the heart in a state of partial aeration, it is clear, 
they say, that this animal is, in this respect, on a par with the higher crustaceans ; 
and since the blood arrives at the heart in the same condition, according to the 
researches of Garner and Milne-Edwards, in Ostrea and Pinna, the great Triton of 
the Mediterranean, Haliotis, Patella and Helix, it can scarcely be doubted that this 
arrangement will be found throughout all the Mollusca.” 
Elaborate as these admirable inquiries deserve to be characterized, they do not 
affect the truth of the leading proposition of Milne-Edwards, that, viz. the visceral 
cavity constitutes a part of, and is an open communication with, the channels of the 
* “ On the Anatomy of Doris," Proceedings of the Royal Society, March 4, 1852. 
