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disc, which uninterruptedly surrounds the central part of the digestive cavity or stomach, 

 without being here, as in other star-fishes, divided by radial septa into several distinct spaces. 

 The whole perivisceral cavity is, as already mentioned, filled with an aquseous fluid which 

 thus immediately surrounds the interior organs. This fluid is however, as has also been 

 shewn in the case of other star-fishes, not purely and simply water, but contains also nume- 

 rous small cellular elements freely suspended in the same. According to their whole nature, 

 these cellular elements are real blood globules; and the said fluid must therefore, even if 

 mixed with considerable quantities of water taken in from without, be considered as real 

 blood. The whole perivisceral cavity represents therefore in the Brisinga — and as I must 

 presume also in the other star-fishes, one single great reservoir of blood. 



I have not succeeded, even with the utmost attention, in discovering any actual 

 blood vessels in the Brisinga; not to speak of the complicated system of veins and arte- 

 ries which, according to the indications of earlier naturalists, is said to be found in some 

 star-fishes. I have endeavored, by repeated dissections and preparations, to discover in the 

 Brisinga the widely ramified dorsal or venous system of blood vessels so minutely described 

 by Tidemann, but always without any result. Whatever may at first have appeared to re- 

 semble such a system has always, when more closely examined, shewn itself to be some- 

 thing quite different; namely sometimes the ligaments and tendinous fibres whereby the in- 

 terior organs, and especially those of the digestive system, are attached to the dorsal skin, 

 sometimes a peculiar folding in the walls of these organs. Neither have I been able to 

 confirm the observations of the earlier naturalists with respect to the ventral or arterial 

 system of blood vessels. Real blood vessels are indeed not to be discovered here, but only 

 a narrow longitudinal canal-like sinus, without any special walls, extending along the ventral 

 furrows of the arms, immediately above the radial nerve-bands, and communicating with a 

 similar narrow circular sinus enclosed between the 2 lamellae of the bucal cuticle nearest to 

 the bucal ring. My investigations of other native star-fishes have given the same negative 

 result. Real blood vessels are no where to be found; according to which I must suppose 

 that the earlier representations of the blood system of star-fish are inaccurate and founded 

 on a less careful examination. There is however one part that has been likewise referred 

 by earlier naturalists to the blood-vessel-system, and which is very distinctly developed and 

 strongly prominent in the Brisinga, that is namely the peculiar membranous organ which in 

 other star-fishes extends from the ventral to the dorsal wall of the disc accompanying the 

 stone canal in its whole course, which is usually regarded as the central organ of circu- 

 lation or heart, whereby the supposed ventral (arterial) and the dorsal (venous) circular 

 vessels are said to be connected. This organ lies, as we know, in other star-fishes together 

 with the stone-canal enclosed between the double lamellae of one of the radial septa which 

 divide the cseloma of the disc like a fan. As there are no such radial septa in the Brisinga, 

 the organ is here enclosed and kept in position by a sheath-like duplicature of the tendi- 

 nous membrane which lines the inside of the skeleton of the disc, and thereby firmly at- 



