VASCULAR SYSTEM. 5 
which were lined with vibratile cilia; from this cavity the vessels sprang. In A/quorea, 
Milne Edwards describes the canals as opening directly into the large and gaping stomachal 
cavity. My own observations accord with those of Will, to the effect that, in most cases 
(among the Gymnopthalmata), there is either a well-defined cavity at the base of the stomach 
into which the vessels open, or an indication of such a cavity. This I regard as homologous 
with the sac so distinctly separated from the digestive tube in the Ciliograda, and into which 
the vessels from beneath the rows of cilia open. The superior cavity in both cases may be 
regarded as an effort towards a specialization of the respiratory system—a view first suggested 
by Will. From it the circulating fluids flow into the gastro-vascular canals, which all run 
without dividing, except in the case of Willsia, into a common marginal vessel, cecal 
projections of which, in several instances, appear to be prolonged into the marginal tentacula. 
Will, however, observes, and I can confirm his remark, that the canals of the tentacles in 
Thaumantias do not communicate with the vessels. The walls of the gastro-vascular canals 
are ciliated. The fluid within becomes coloured, according to the food taken by the animal. 
I have seen it in a Thaumanitias fed upon small crustacea turn completely yellow. 
The system of vessels, partly nutritive, partly respiratory, proceeding directly from the 
stomach, or from a cavity opening directly into it, may be regarded as a good instance of 
phlebenterism. Dr. Will, however, regards it as an aquiferous system, and describes a 
circulatory system distinct from it. He asserts that in Geryonia all the water-vessels are 
accompanied by blood-vessels, which spring from the sides of the stomach, and proceed to its 
base, there to run alongside of the water-vessels. He states that they are distinctly to be 
recognised on both sides of the latter, especially when they contract ; then the blood-vessels 
remain expanded, and appear much thicker. At the circular marginal water-vessel the blood- 
vessel is usually observed only on one side, and that at the lower. Sometimes there appears 
a narrow margin, filled with blood-corpuscles at the upper edge. “The contents of the 
blood-vessels usually consist of a clear fluid, in which a great number of finely granular 
corpuscles, of a diameter from 1-400—1-500”, are floating.” He observed similar blood- 
vessels in Thaumantics. 
Aware of these observations, and of the accuracy of the observer, I made every endeavour 
to satisfy myself on the matter with the species of several genera. But though I sometimes 
fancied I saw such vessels, in the end I came to the conclusion that the appearances were 
deceptive. No such vessels appear to have been noticed by Wagner or Milne Edwards. 
Will described similar vessels distinguished by this red colouring in Beroe. I have seen the 
appearances to which he alludes, but could not satisfy myself of their vascular nature. Frey 
and Leuckhart, also, with Will’s observations before them, have sought in vain; their remarks 
upon this subject are so much to the point that I quote them verbatim: “ Our attention whilst 
investigating was likewise directed to this point, but without discovering the characters 
mentioned (i. e. by Will). Neither in Cydippe, nor in Geryonia, nor in Cyanea, did we 
succeed in discovering particular blood-vessels in addition to the canals of the abdominal 
cavity. We may assert, with particular distinctness, that the species (new?) of Geryonia 
observed by us is altogether deprived of a peculiar system of blood-vessels, although Will 
has recognised such in Geryonia pellucida, described by him, and from which our species 
is principally distinguished only by having marginal tentacles of equal length. A result, 
