﻿58 proceedings of the [Dec., 1856. 



been, from his drawing, though not noticed in his description, a 

 hyaline body in the upper part of the proboscis, which, however, 

 seems to be more conspicuous in its continuation over the sexual 

 lobes than in our own species. 



Turritopsis nutricula, as I propose to call the subject of this 

 paper, is in shape a deep bell, whose lateral outline is somewhat 

 emarginate near the summit of the dome, and this latter appears 

 almost a flat surface except while the animal is freely swimming, 

 when a slight conical apex is visible. See PL 4, ff. 3, 4, 5. This 

 bell is transparent, yet not so clearly so as the disk of Thauman- 

 tias or Hippocrene, since the large size of the muscular cells give 

 it a corrugated appearance and refract the rays of light along their 

 edges to a greater extent. They are not arranged in continuous 

 rows, but are apparently felted together, their longitudinal diame- 

 ter always parallel to the marginal tube. The internal surface of 

 the bell is covered by an epithelium of very small cells, on which 

 1 have not observed cilia, yet I am inclined to think they are pre- 

 sent. Overlying the layer of muscular cells is a tissue composed 

 of larger and more oblong cells than those of the epithelium on the 

 inner surface. See PI. 4, fig. 15, A and B. This, so far as I have 

 been able to discover, is the external layer, and on its outer surface 

 are discernible only a few scattered circular cells, fig. 15, a. The 

 only indication of vertical fibres which I have been able to iden- 

 tify are the four longitudinal seams already spoken of, as repre- 

 senting the longitudinal bands of Tunis, but even now I am 

 unable to say positively whether they are muscular fibres or not. 



The disk is traversed by four rather flat and broad vertical chy- 

 miferous tubes which enter it at its junction with the clear cellu- 

 lar mass forming the upper part of proboscis. (PL 4, fig. 1.) 

 Arching slightly outward these descend to the tentaculated margin, 

 where they communicate simply with the circular canal, i. e., they 

 form no bulb-like enlargement. This latter canal is of about the 

 same width as the vertical, and presents the same flattened ap- 

 pearance. 



The tubes are lined with a granular tissue, somewhat more 

 opaque white than the remainder of the bell. They are, therefore, 

 conspicuous, and at times are filled with a rapid current, densely 

 crowded with granules held in suspension, which appear to be 

 ur^ed onward by ciliary action. An interval decidedly wider than 

 Qi 1 in these Medusas, intervenes between the circle of tentacuia 

 and ..he marginal canal. The tentacuia, as usual, spring from the 



