388 EVENINGS AT THE MICEOSCOPE. 



are now in view in the field of the microscope. 

 You see a number of bodies, which Dr. Wright calls 

 ophidian or spiral polypes, and which, as he truly 

 observes, are " like small white snakes, closely coiled 

 in one, two, or three spirals, and grouped immediately 

 round the mouth of the shell." The habits of these 

 polypes are still stranger than their forms. " "When 

 touched, they only draw their folds more closely 

 together. But if any part of the polypary, however 

 distant from them, be irritated, the spiral polypes 

 uncoil, extend, and lash themselves violently back- 

 wards and forwards, and then quickly roll themselves 

 up again ; and that not irregularly or independently of 

 each other, but all together, and in the same direction, 

 as if moved by a single spring. A violent laceration 

 of the polypary causes these polypes to remain extend- 

 ed and stretched like a waving and tremulous fringe 

 across the mouth of the shell, for several minutes. The 

 ophidian polypes (evidently a barren modification of 

 the reproductive polype) are never found in any 

 other situation on the polypary than in that before de- 

 scribed, or round the margins of accidental holes in 

 the shell. They have no mouth, and the tentacles are 

 rudimentary. The walls of the body are very trans- 

 parent, from the extreme vacuolation of the inner 

 tissue. Tlie muscular coat, as might be expected from 

 the active movements of the polypes, is highly de- 

 veloped, and forms a beautiful object on the dark 

 polarized field of the microscope, each spiral coil shin- 

 ing out as a bright double ring, divided by four dark 

 sectors. The outer tissue of the whole body and ten- 

 tacles is crowded with the larger thread-cells. The 

 ophidian polypes are, doubtless, organs of defence or 



