14 JELLY-FISH, STAR-FISH, AND SEA-UIICHINS. 



'• Archiv. f. Naturgesclnclite," 1851, b. i. ; McCrady, 

 *■' Descriptions of Oceania, etc.," " Proceedings of the 

 Elliot Society of Natural History," vol. i., 1S59 ; 

 L. Agassiz, " Contributions to the Acalipha) of 

 North America," "J^Iemoirs of the American 

 Academy of Arts and Sciences," vol. iii., 18G0, 

 vol. iv., 18G2; Leuckart, "Archiv. f. Naturge- 

 schichte," Jahrg. 38, b. ii., 1872 ; Hensen, " Studien 

 liber das Gehororgan der Decapoden," " Zeitchr. 1 

 wiss. ZooL," bd. xiii., 1863 ; Semper, ** Reisebcricht," 

 " Zeitschr. f. wiss. ZooL," bd. xiii. vol. xiv. ; Glaus, 

 *' Bemerknngen iiber Glenophoren nnd Medusen," 

 "Zeitschr. f. wiss. ZooL," bd. xiv., 18G4 ; Allman, 

 "Note on the Structure of Gertain H3^droid 

 MeduscV "Brit. Assoc. Rep.," 1807; Fritz Muller, 

 " Polypen und Quallen von S. Gatherina," " Archiv. 

 f. Naturgesch.," Jahrg. 25, bd. i., 1859; also "Ueber 

 die Rand-blaschen der Hydroidquallen," " Archiv. 

 f. Anatomic und Physiologic," 1852 ; Haeckel, 

 "Beitrage zur Naturgesch. der Hydromedusen," 

 1865; Eimer, "Zoologische Untersuchungen," Wurz- 

 burg, " Verhandlungen der Phys.-med. Gesellschaft," 

 N.F. vL bd., 1874^. 



The most important of these memoirs for us to 

 consider are the two last. I shall subsequently 

 consider the work of Dr. Eimer, which up to this 

 date was of a purely physiological character. Pro- 

 fessor Haeckel, who made his microscopical obser- 

 vations chiefly upon the Geryonidro, desciibed the 

 nervous elements as forming a continuous circle all 

 round the margin of the umbrella, following the 

 course of the radial or nutrient tubes throughout 



