THE DISK. 85 



SO transparent, so shadowy, that a friend to whom I 

 shewed it aptly called it the soul of the zoophyte. 

 There is something in it also that reminds me of the 

 pappus of a dandelion floating on the hreeze. 



Immense numbers of these tiny sylph-like creatures 

 were successively produced from the Laomedea in the 

 glass jar, so that the water at length seemed quite 

 alive with them ; but I could not find that a single 

 individual either became stationary, or changed its 

 form, or grew. In the course of a day or two they all 

 died. 



I will now describe one of them more in detail. 

 Under the microscope it is seen to be a pellucid 

 colourless disk or umbrella of considerable thickness, 

 about ^th of an inch in diameter in its average state 

 of expansion. Its substance has a reticular appear- 

 ance, probably indicating its cellular texture. Inter- 

 nally, the disk rises to a blunt point in the centre, 

 w^hence four vessels diverge to opposite points of the 

 margin. These form elevated ribs, the surface being 

 gradually depressed from each to the centre of the 

 interspace. (See fig. 1.) Externally* the centre of 

 the disk is produced into a fleshy foot, having a 

 narrow neck, and then expanding into a sort of 

 secondary disk, of a square form with the angles 

 rounded. (See figs. 1 and 0.) This organ appears to 

 be muscular, or at least it is capable of varied precise 

 and energetic motions. The angles, which correspond 

 in their direction to the four internal ridges, are very 



*I use the terms "internally" and "externally" only with reference 

 to the appearance of the embryo : this process is the representative of 

 the peduncle of a Medusa, vrhich is within the concavity of the umbrella. 



I 



