610 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
Like that of the Echinus it is confined to the alimentary canal. My dissections have 
never demonstrated more than one vessel extending back from the oesophageal ring, 
over the superior surface of the tube. If it be an artery there is no correlate vein. It 
is traceable along one border only of the canal, coinciding with the spiral convolutions 
of the latter as far as the anal outlet; no capillary system is traceable at its end ; no trace 
of vessels of any description can be discovered in the parietes of the alimentary canal. 
According to my observations, again and again repeated, the interior of the blood- 
vessel of the Sipunculidae generally is lined with vibratile epithelium ; of the truth of 
this fact, extraordinary though it be, I am persuaded. The corpuscles of the fluid 
contents of this vessel were found in every species to be the exact counterpart of those 
of the fluid of the visceral cavity. They are identical in colour, in diameter, in Jigure, 
and in structure, figs. 4, h, 6 and 7*. But in the fluid of the blood-vessel they are more 
numerous relatively to the bulk of the fluid than they are in that of the visceral cavity. 
If the true-blood penetrated into the substance of the solids by means of capillary vessels, 
there would in the Sipuncle exist no difficulty in tracking its course by means of the 
corpuscles. It is certain that in these Echinoderms it is not distributed throughout the 
solid parietes of the alimentary canal. The movement of the corpuscles, which is 
oscillatory, cannot be traced in any case beyond the limits of the primary trunk. In 
the Vermigrade Echinoderms, then, as in the Echinidae and Asteriadse, the system of 
the blood-proper is a partial and local development. It has few, if any, systematic rela- 
tions. It fulfils but a very insignificant part in the nutrition of the organism. In the 
particular of the red colour of the blood-proper the Sipunculidse approximate the Anne- 
lida. In the character however of the presence of corpuscles — organized cells — in the 
blood (on the supposition that it forms an independent system and not a part of the 
chylaqueous), they transcend the latter class and approach the higher Articulata. 
The corpuscles of the fluids in the vessel and in the visceral cavity present a 
pink tinge. Each corpuscle is flat and irregularly oblong; remarkable uniformity 
prevails in their size and structure, figs. 4 and 5. Each exhibits a bright, small, highly 
l efractive nucleus ; in some cells a second may be seen. The dimensions of this 
nucleus are disproportionately small in relation to the containing cell. The colour 
is dissolved in the fluid between the nucleus and involucrum. These corpuscles are 
* Although my observations are quite at variance with those of Dr. Peters as regards the number and 
distribution of the blood-vessels, our researches on the corpuscles of the fluids are mutually confirmatory. 
“ Betrachtet man dieses Gefiiss mit einer starken Loupe, so sieht man einen Strom von Kdrperchen, welcher sich 
nach dem Schlund hin langsam fortbewegt, wiihrend man bei dieser Vergrosserung in den beiden danebenliegen- 
den rothen Geftissen noch gar keine Kdrperchen oder Bewegung wahrnehmen kann. Bringt man dagegen den 
mit Wasser gefiillten Darm eines frischen Thieres unter das zusammengesetze Mikroskop, bei einer etwa 50- 
maligen Vergrosserung, so sieht man in dem mittleren gelblichen Gefiiss die schdnste Wimperbewegung, 
wodurch die Kugeln, welche sich jetzt deutlich als Eier erkennen lassen, vorvvarts getrieben werden, in den 
beiden rothen Seitengefassen dagegen, Blutkdrperchen von derselben Form wie in dem Kdrpergefiiss, welche 
sich ohne Wimperbewegung, und unregelmiissig nach vom hin bewegen. Sehr oft liess sich nichts weiter 
unterscheiden, als dieser einfache eierfiihrende Canal mit don beiden Gefiissen zur Seite.” Ueber die 
Fortpflanzungsorgane des Sipunculus. Von Dr. William Peters, Muller’s Archiv, 1850. 
