THE BLOOD OF MAGELONA. te 
body-cavity. In Phoronis the pigment is hemoglobin, as 
Lankester showed by its spectrum, and is not hemerythrin, 
as Krukenberg assumes. In Phascolosoma elongatum 
Schwalbe describes the tint as light rose or faint greyish red 
(matt graurothlich), which on oxidation grows darker, and finally 
becomes “ burgunderrothe.” This description of the colour 
scarcely agrees with that of Magelona, nor does that given 
by Ehlers and Keferstein for other members of the group— 
Sipunculus and Priapulus,—for they term the colour of 
the body-fluid ‘ wine-red;” but in Sipunculus nudus at 
any rate, as I can testify from my own observations, the tint 
is very close to that seen in Magelona. 
6. Relation of Vessels to Celom.—The fact that in 
the thorax the ventral vessel dilates to such an enormous extent 
as to nearly obliterate the ccelom is a very interesting and im- 
portant piece of evidence in favour of Professor Lankester’s 
suggestions (‘ Quart. Journ. Mic. Sci., xxxiv, 1893) as to the 
manner in which the heart of Arthropods, with its series of 
ostia for the entrance of blood, has been derived from a Cheeto- 
pod vascular system, owing to the enlargement of the afferent 
vessels or veins, till the latter fuse with one another to form a 
great “ pericardial blood sinus,’’ to the exclusion of the ceelom. 
Here, in Magelona, we have a great dilatation of the ventral 
vessel and lower part of the “ afferent” vessel leading upwards 
to the dorsal vessel. This great lateral dilatation (J. ext.) com- 
municates with the ventral vessel just behind the septum, 
between consecutive segments, by a comparatively narrow 
opening, as shown in the figure. If this dilatation extended 
further upwards to the dorsal vessel we should have a condition 
closely approaching that of the Arthropod vascular system. 
This ventral vessel of Annelids no doubt corresponds to the 
great ventral blood sinus of Astacus, &c., whence the blood 
makes its way up to the heart, either directly or by way of 
the gills. 
I hope, in a later contribution, to give a further account of 
the vascular system of this interesting worm, Magelona. 
