605 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
Speaking of the difficulty experienced by M. Quatrefages in detecting the vessels 
of the intestine in Synapta Diwernoea, Muller incidentally remarks, “ Denn man 
darf die fVassergefdsse nicht mit den Blutgefdssen identificiren, welche die voin Darin 
kommende Nahrungsfliissigkeit enthalten.” In another place he speaks of “Die 
Unabhangigheit des Wassergefasssystems und des Blutgefasssysteins von einander*.” 
From a careful study of the memoirs of Muller, it has appeared to me to be cer- 
tain that he has never succeeded in tracing the blood-system to its periphery even in 
the Synaptse. He has only been able to show that a branch or two in some species 
is given off from the trunks at the roots of the tentacles, to be distributed over the 
integument. He nowhere offers a single remark as to the colour or composition of 
the blood. In commenting on the observations of Quatrefages, he seems disposed 
to deny the existence of cilia on the internal lining membrane of the channels of the 
true-blood. 
It should then be remembered that Muller, like Tiedemann, has succeeded in 
demonstrating only the central trunks of the blood-vascular system. In animals so 
large, with vessels so considerable in diameter, the question may be emphatically put. 
Why to an expert dissector should this difficulty of tracing the circumferences of the 
system exist ? In every other class of animals in which a blood-system exists at all, 
nothing is so easy as to observe its peripheric segments. In the most delicate An- 
nelid the capillary extremes of this system are readily detected. I reply, that in the 
Echinoderms the blood- system has not yet evolved a circumferential plexus. This is 
one of the characters of imperfection which marks the first appearance of this system 
in the animal series. It is because Muller, as the first anatomist of the age, has 
reached by a distinct channel of inquiry, impliedly, the very same results with those 
which are presented in this paper, that I have digressed in the preceding remarks 
from a consideration of the contents of the blood-system to that of the system 
itself. 
I have instituted laborious dissections on many hundred specimens into the blood- 
vascular and water-vascular system of the Asteriadse, Echinidse and Sipunculidsc. 
No Holothuridan species, in a fresh state, has yet fallen under my observation. I 
regret this circumstance the more, for in these genera the blood-system attains a 
higher degree of development than in any other of the Echinoderms. 
The result of my own researches may be first conveniently stated under the form 
of the following propositions : — 
1st. The blood-vascular system in the Echinoderms is not an independent and 
c/o^cf/ system of conduits; it is rudimentary and imperfect in its peripheral portions. 
2ndly. The internal lining membrane of its channels is ciliated, a character which 
separates the blood-system of this class from that of every other in which it is known 
to exist, while it significantly attests its rudimentary condition. 
3rdly. The fluid contents of the blood-vascular system are chemically and mor- 
* Berichtigung imd Nachtrag zu den Anatomischen Studien iiber die Echinodermen. 1850. 
