266 .LCIIHSDDEIIMATA. 



to receive relatively large bodies, even fishes, into the wide oesophageal 

 tube, and to digest them. Although the average size is small, some 

 of them, as Cestum, Eucharis, reach the length of a foot. 



Fam. Cydippidae. Body slightly compressed, spherical or cylindrical, with 

 extremely regular development of the swimming plates. Their structure is 

 therefore apparently octoradial . They possess two tentacles ; the vessels of the 

 stomach and swimming plates end blindly. Cydippe liormiplwra Ggbr. = 

 Ilornnpliora plumosa Ag., Mediterranean. Eselischoltzia cordata Kb'll., 

 Mediterranean. 



Fam. Cestidae. Body elongated to the form of a band in the direction of the 

 sagittal plane. Two tentacles. Vex ilium parallelum Fol., Canary Isles. 

 Cestum, Verier! s Less., Venus' Girdle, Mediterranean. 



Fam. Lobatse. The laterally compressed body possesses two umbrella-like 

 lobes near the mouth, and has relatively small tentacles. Eurkampliaca vexil- 

 llgera Ggbr., Mediterranean and Atlantic Ocean. Cliiaja papillosa, M. Edw. 

 (Alcinoe paplllosa Delle C\\. = Xeapolitana Less.). Mediterranean. 



Fam. Beroidse. Characterised by the laterally compressed body with fringe- 

 like appendages on the periphery of the polar spaces ; without tentacles. 

 Beroe Forskalii M. Edw. (albescens and rufesccns Forsk.), Idyiopsis Clarlii 

 Ag., Pandora Flcmmingii, Esch. 



CHAPTER VIII. 



ECIIIXODERMATA.* 



Animals with a radial, usually pentamerous arrangement. They 

 possess a skin tearing spicules and indurated by calcareous deposits, a 

 digestive canal, a water-vascular apparatus, and a true vascular system. 



The radial arrangement of the Echinoderms was for a long time 

 held to be a character of typical value, and was the principal reason 

 why, since the time of Cuvier, the Echinoderms were included in 

 one group, the Radiata, with the Medusre and Polyps. ^It is only 

 in recent times that R. Leuckart has effected the separation of the 

 Echinoderms from the Ccelenterates. 



The organization of the Echinoderms does in fact appear so different 

 from that of the Ccelenterates, and seems to belong to a so much 

 higher grade of development, that the combination of the two groups 



* Fr. Tiedemann, " Anatomic der Rb'hrcnholothurie, des pomeranzfarbenen 

 Seesternes und des Stein-Seeigels," Heidelberg, 1820. Joh. M tiller, " Uber den 

 Bau der Echinodermen," Ab'h. der Berl. Akad, 1853. Joh. Mtiller. " Sieben 

 Abhancllungen Uber die Larven und die Entwickelung der Echinodermen." Abh. 

 der Berl. Akad, 1846, 1848, 18.9, 1850, 1851, 1852, 1854. A. Agnssiz, " Embryo- 

 logy of the Starfish," Contributions, etc., Vol., V. 1864. E. Metschnikoff, 

 "Studien iiber die Entwickelungsgeschichte der Echinodermen und Nemer- 

 tinen," St. Petersburg, 1^69. H. Ludwig, " Morphologische Studien an 

 Echinodermen," Leipzig 1877 and 1878. 



