614 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
the latter. Its ‘ molecular base’ is like that of the latter, it affords abundant crystals 
of chloride of sodium like the latter. These and other reasons have satisfied me that 
the bulk of the fluid contained in the peritoneal cavity of Asterias is derived from 
that which enters throug'h the mouth into the digestive caeca, in which the first 
phase of the digestive process is performed ; the second and subsequent changes, by 
which it is raised to a higher grade of organic composition, occur during its sojourn 
in the peritoneal space, into which it passes by exosmosis, from the digestive caeca. 
If the individual be placed for some time in pure sea-water, destitute entirely of 
organic material, the digestive caeca and the peritoneal space will be found to con- 
tain the same fluid, almost completely free from all traces of organic substances*. 
* I have instituted, at great labour to myself, a series of variously devised observations, with a view to set 
at rest, if possible, the question relative to the real source and nature of the fluid contained in the peritoneal 
cavity of Asterias Rubens, and through this example, to close the controversy, in relation to all other Echino- 
derms. First, then, is it salt-water ? if so, how does it gain admission into the cavity in which it is contained ? 
For answer, I affirm that under the ordinary circumstances under which these animals are examined, it is 
almost pure sea-water ; but in the natural state (that is, when the water taken into the digestive organs 
contains, as it always does in their native habitat, organic substances, living and dead), it is a chylaqueous 
fluid, in which the first steps of vitalization and organization have commenced, and that in Asterias it is thb 
REAL SUBJECT of the respiratory process, the true-blood not being brought in any \vay under the agency 
of the external element. This answer applies to all Echinoderms. The existence and offices of this fluid 
explain the fact of the suppressed or rudimentary development, under which the true-blood system obtains in 
these animals. The latter performs merely the functions of pabulating very partially the solid elements of 
structure ; the chylaqueous fluid is the veritable seat of the blood-making and respiratory processes. And 
2nd, I reply that every method of examination fails in proving the existence of any pores or orifices of an)’ sort 
whatever in the integumentary boundaries of the peritoneal space in Asterias. Muller has arrived at the same 
conclusion. 
He remarks, “ Die respiratorischen Rbhrchen auf dera Rucken der Asterien, welche mit der Bauchhohle 
communiciren, sollen zufolge der Injectionen von Tiedemann am Ende offen sein, und zum Wechsel des 
Wassers der Leibeshbhle dienen. Nach Ehrenberq dagegen sind die Rbhrchen am Ende geschlossen, er 
sowohl als Sharpey sahen die Strbmungen im Innern am Ende umkehren. An jungen lebenden Exemplaren 
des Asteracanthion violaceus sah ich dasselbe, und es gelang mir nicht eine OefFnung wahrzunehmen.” 
(Muller, Archiv, 1850, 121.) 
On the contrary, in the larvae of the Echinoderms, Agassiz maintains, on the ground of his outi obsen^ations, 
that the external water passes by a direct stream into the cavity of the body. Such an improbable statement 
requires however to be carefully verified. These are the words of Agassiz ; — “ Bei den niederen Thieren 
besteht eine innigere Verbindung zwischen dem Innern und dem umgebenden Medium, als in einer der hoheren 
Classen. Das Wasser stromt durch unzahlige Poren in ihren Kbrper und fiillt seine Hbhle. Einige von 
diesen Rbhren nehmen eine sehr eigenthiimliche Anordnung in den Echinodernien an und dienen zugleich zur 
Ortsbewegung. Da dieser Apparat einer der ersten ist, welche in dem Jungen ercheinen, so muss ich seine 
Struetur bei den Seestemen anfiihren. Die hohlen Fiisschen sind in der Durchschnitts-Abbildung herab- 
hangend dargestellt. So haben wir einen hydraulisehen Apparat von sehr zusammengesetzter Natur,” &c. 
Injeetions carefully thrown into the peritoneal space distend, and enter into the membranous projections 
of the integument already described, but it never escapes externally, exeept through a rupture of the delicate 
containing parts. A coloured thin fluid (i. e. sea- water) cautiously injected into the cseca through the mouth 
(first laying open the integuments), will distend these parts, and invisibly and without ruptui-e slowly transude 
into the peritoneal space ; but injection consisting of size diluted with water, will not escape out into the 
