194 



The Polypidom in luxuriant specimens is five or six inches in 

 height, bearing from one hundred and twenty to one hundred and 

 fifty polyps. It is of a dark, brownish horn color, with polished 

 surface, looking at a little distance like horsehair, and when 

 seen waving gently in the water, with its bright red polyps, it 

 has the appearance of a beautiful flowering plant. The upper 

 portion of each tube, (from which the polyps rise,) is surrounded 

 with rings. 



The body of the polyp, above the tube, is ovoid oblong. The 

 mouth is undoubtedly at the extremity, though in numerous 

 examinations with a high power I have been unable to detect it. 

 Near the base is a circle of long, slender, nearly cylindrical 

 arms. These on their exterior half show no trace of fibres but 

 are crowded with oval cells containing in each an organ perhaps 

 similar to one to be presently described in the upper arms. It is, 

 however, so minute that a power of six hundred diameters fails 

 to show its form. The interior half of the arm has none of these 

 cells but is strongly marked with transverse lines of fibres ; that 

 they are muscular is not proved. From within this circle of 

 arms spring the ovarian vesicles, from which undoubtedly the 

 medusa form of the polyp is developed, though this development 

 has not yet been observed. They are ovoid, equalling the arms 

 in length. 



The arms of the second row are much shorter and of less 

 number. Each consists of a slender pedicle surmounted by a 

 large, globular head. The head is studded with numerous ovoid 

 cells, with the broader end outward. The cells are seen to con- 

 tain each a minute filament. On the application of pressure, the 

 cell opens and the filament is protruded and at the same moment 

 expanded into an exceedingly acute barbed arrow-head. The 

 delicacy of this organ may be estimated from the fact, that the 

 cell which contains it is less than one twentieth of a millimetre in 

 length. The mechanism by which the animal is able to protrude 

 and retract the dart is too much attenuated to be visible by any 

 magnifying power I possess. The cell is lined with an extremely 

 thin membrane, which possibly may assist in the operation, but 

 it apparently would not be able to draw down the wide-expanded 

 barbs and confine them to the shaft of the dart. A higher mag- 

 nifying power may yet solve the question. The dart is similar 



