VASCULAR SYSTEM. 5 



which were Uned with vibratile cilia ; from this cavity the vessels sprang. In Mqiwrea, 

 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, csecal 

 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 Thaumantias 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 Thaumantias. 



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 Cyancea, did we 

 succeed in discovering particular blood-vessels in addition to the canals of the abdominal 

 cavity. W^e 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. 



