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by the apparently well-ascertained (?) fact that water is admitted by the 
madreporite to mix with the coelomic fluid of the Echinoderms. 
The supposition that there may be a correlated out-pouring of the 
contents of the vascular system is favoured by the undoubted fact that 
the coelomic fluid is occasionally shed through the dorsal pores of the 
Earth-worm. 
In spite of the fact that such an in-taking and out-shedding of 
fluid would not, were it capable of demonstration in the Mollusca, 
stand as an isolated example of a somewhat startling physiological 
process — I have been led to entertain the strongest doubts as to its 
occurrence in Mollusca ever since I ascertained the existence of Hae- 
moglobin in the plasma of the blood-fluid of the Gastropod Planorbis 
and of oval nucleated corpuscles richly charged with Haemoglobin in 
the blood of the Lamellibranch — Solen legumen. 
An examination of the living specimens of Solex legumen made by 
me at Naples in 1872 was absolutely convincing as to the fact that in 
that Lamellibranch the blood-fluid is under no circumstances shed 
from any pores or apertures in the animal’s body, so long as the surface 
is uninjured. 
It was equally conclusive as to the fact that complete distension 
of the foot is produced in that animal without any admission of water 
to the vascular system, by the simple mechanism of a rapid flow of the 
deep-red-coloured blood from the mantle and body of the Lamelli- 
branch into its foot. 
It was easy to observe the to-and-fro movement of the blood when 
a specimen of Solen legumen was taken out of the water and held in 
the hand, owing to the deep red colour of the blood caused by its cor- 
puscles. The whole vascular system can be readily traced in this La- 
mellibranch owing to the transparency of the tissues and the red co- 
lour of the blood. 
With regard to the Gastropoda — the same kind of evidence is 
afforded by Planorbis corneus. The red-coloured haemoglobinous fluid 
is under no circumstances shed from the body of that animal unless its 
surface is wounded. Similarly there is no evidence of a dilution of the 
red-coloured fluid (such as would be afforded by its acquiring a paler 
tint) when the Planorbis is made to expand and retract its foot repeat- 
edly. Were water admitted to the blood in the act of expansion of the 
foot, the repetition of this act would necessarily lead to a dilution of 
the haemoglobin and a diminution of the red colour of the blood-fluid. 
2) The question of the out-pouring of the vascular fluid of Mol- 
luses must be treated as distinct from that of the introduction of water 
through pores on the surface into the blood-system. 
