Chap. I. 



ADULT MEDUSA OF CORYNE MIRABILIS. 



211 



the human spermatic particles than any others. At one end there is a pear- 

 shaped body {Fig. 25^), from the broad part of which a very slender and long 

 filament arises. The filament is about eight times as long as the pear-shaped 

 part, and trails behind when the whole is swimming. 



SECTION V 



hang 

 forming 



Fig. 28. 



ADULT MEDUSA OF CORYNE (SARSIA) MIRABILIS. 



The form of Sarsia mirabilis is very peculiar, and remarkably well adapted for 

 its rapid movements. It is somewhat bell-shaped, or hemispherical; with the upper 

 vault broad and flat, and the sides rather prolonged, assuming 

 even, sometimes, in the relaxed state, a more or less cylindrical 

 form; when contracted, the whole body has an almost hemis- 

 pherical shape, and may, at times, really assume the appear- 

 ance of a nearly globular mass. All these forms pass so 

 rapidly from one into another, that it is exceedingly difficult 

 to say which is the more natural. When jiausing, motionless, 

 in the midst of the water, these medusas have the most regular 

 hemispherical form; the four arms are then stretched at right 

 angles with the lower margin of the animal, for a short 

 dist<ance, and their extremity hangs vertically downwards, for 

 perhaps two or three times the length of the greatest 

 diameter of the central mass. After remaining for a while 

 immovable in that position, the walls of the body may relax, 

 the arms elongate, the sides hang loosely downwards, and the 

 whole body assume a more cylindrical form : when the arms 

 straight downward in graceful undulations, and without 

 any marked angle with the base of the animal. 

 In this state of relaxation, the tentacles may elongate for 

 three, four, and even more than five times the length of the 

 bell-shaped part of the animal (wood-cut 30, p. 212). Some- 

 times they extend to an extraordinary length (wood-cut 28). 

 But if, suddenly starting from this inactive position, the body 

 contracts powerfully to move onward, it assumes an almost 

 entirely spherical form, the thinner margins contracting more 

 extensively than the main mass, and shutting almost entirely 

 the lower opening of the body. The arms naturally follow, in their undulations. 



