290 CONTRIBUTIONS TO THE NATURAL HISTORY 



Fig. 7), but never to the extent which is observed naturally in Staurophora, unless in 

 very powerful contractions after death, or during the violent spasmodic contractions pre- 

 ceding death, when specimens are sometimes seen to assume nearly the form of a four- 

 rayed star (Plate VI. Fig. 8) when viewed from below, with a rounded disk above. 



The movements of the animal are very graceful, and rather sustained. They are not, 

 however, so powerful and energetic as in Sarsia, nor so abrupt and by starts as those of 

 Hippocrene. It proceeds onwards or moves in all directions, upwards, downwards, or 

 sideways, or changes its course in a direction opposite to that in which it was previously 

 moving ; and in all these evolutions it performs its movements in a very gentle and quiet 

 way, full of grace and elegance, and has nothing of the quick, brisk, and I may say vio- 

 lent, movement which is so characteristic of Sarsia, — displaying in this mode of locomo- 

 tion the difference of temperament there is between the species of the two genera, 

 and indicating milder habits, and a less rapacious or voracious disposition. 



Indeed, Tiaropsides are never seen to attack Medusae larger than themselves. They 

 rather feed on smaller prey, as very young Ephyrae, or on small particles of decaying an- 

 imal matter. The shortness of their proboscis, and the lobed form of its margin, are in 

 accordance with the indications derived from their way of moving. They seem rather 

 adapted to suck their prey, than to take strong hold of it with a powerful proboscis, as is 

 the case in Sarsia. They appear always in large numbers, gently sailing about, hither 

 and thither, in the midst of the waters, with slight indications of activity, and are fre- 

 quently chased by Sarsia, which prey largely upon them. 



These little animals are the free Medusa state of animals very common on these shores, 

 which have been long known under the name of Campanularia, and which are supposed to 

 belong to the class of Polypi. But as I have been able to trace the whole transformation 

 of successive generations of these animals, I shall in another part of this paper give a 

 complete history of their development, limiting myself here to describing the particulars 

 of their structure, in the full-grown condition of the Medusa state. 



Like all other naked-eyed Medusae, Tiaropsis has a gelatinous disk with a central 

 digestive cavity, from which arise chymiferous tubes (Plate VI. Fig. 5), diverging at right 

 angles towards the margin, where they unite with the circular tube extending all round 

 the lower outline of the body along the base of the tentacles. This circular tube com- 

 municates freely with the vertical ones, and through these with the central cavity, so 

 that chyme, which is elaborated in the main central cavity, is circulated to and fro 

 in these tubes, without, however, passing into the tentacles, which are not hollow, as 

 in Sarsia, but solid, as in Staurophora and Hippocrene. Within the margin, on the inner 

 side of the circular tube, a thin nervous cord is observed, as in the other genera of 

 this family. 



