25 



distinctly marked with transverse stria, and are assembled in fasci- 

 culi of various sizes and lengths. 



ADDENDUM TO THE FOREGOING PAPERS. 



As the nature of these marginal bodies is perhaps still obscure, 

 and its determination a matter of interest, I have endeavoured to 

 collect all the more important observations hitherto made with re- 

 gard to them, and the result is as follows. 



Though noticed and imperfectly described and figured by Ehren- 

 berg and Milne -Edwards, no connected account of the varieties pre- 

 sented by these bodies in various species seems to have been afforded 

 before that given in Dr. Will's ' Horae Tergestinse,' published in 1844 ; 

 a work which cannot be too highly praised. The substance of what 

 he says of the marginal bodies, termed by him " auditory capsules," 

 is included in the following summary. 



"1. In Cydippe the auditory capsule is pedunculated, and consists 

 of a simple but tolerably thick membrane and a round mass of 

 crystals, of a reddish-gray colour in Beroe, but white in Eucharis 

 and Cydippe. Between the inner surface of the cyst and the crys- 

 talline mass is a transparent interspace of considerable width, which 

 appears to be filled with a fluid, for the cyst is not only always dis- 

 tended to the utmost, but also changes its figure according to the 

 shortening or extension of the infundibulum ; in the former instance 

 becoming globular, in the latter elongated. The granules are slightly 

 transparent, roundish or of a compressed reniform shape. Examined 

 in oil of turpentine their form becomes more distinct. They are 

 dissolved with effervescence by muriatic acid. Their number varies 

 according to age and the species. In' the auditory capsule of Beroes, 

 two inches long, I have counted about two hundred, and as many in 

 Eucharis, but in Cydippe not more than twelve to fifteen." 



" I have never succeeded in observing any motion in these crystals, 

 or ciliary movements on the inner surface of the cyst, as has been 

 observed by Kolliker and Siebold in the Mollusca, either in the 

 Ctenophorous or Discophorous Medusa, although I have employed a 

 good microscope by Schieck, and sufficiently great magnifying 

 powers (I. c. p. 45 and 46)." 



He was equally unsuccessful also in observing any motion in the 



TRANS. MIC. SOC. VOL. HI. E 



