266 ECHINODERMA.TA. 



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

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

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



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

 extremely regular development of the swimming plates. Their structure is 

 therefore apparently octoradial . They possei-s two tentacles ; the vessels of the 

 stomach and swimming plates end blindly. Cijd'tppc- liorwipluira Ggbr. = 

 JToriiiijilioi-a plu in nxa Ag.. Mediterranean. Ewlxrholtzia cor/hitu Koll., 

 Mediterranean. 



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

 sagittal plane. Two tentacles. Vr.eilhnii- pai-nUrlum Fol., Canary Isles. 

 ('/xfmii I'fnei'ix ].css., Venus' Girdle, Mediterranean. 



Fain. Lobatae. The laterally compressed body possesses two umbrella-like 

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

 ligern Ggbr., Mediterranean and Atlantic Ocean. CMaja papilloga, M.. Edw. 

 (AlcinSe papillosa Delle Ch. = J\V/Ai7/fr*. Less.), Mediterranean. 



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

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

 Bcrbc Forshalii M. Edw. (_tilln-xi-i-nx and rnfi-xci-nx Forsk.), Itlyio^xix Cl<trl;j 

 Ag.. Pandora Jft&nmAngii, Esch. 



CHAPTER VIII. 



ECHINODERMATA.* 



Animals with a radial, usually pentamerous arrangement. They 

 possess a skin bearing 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 Medusae 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 Ceelenterates, and seems to belong to a so much 

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



* Fr. Tiedemami, ''Anatomic der Rohrenholothurie, des pomeranzfarbenen 

 Seesternes and des Stein-Seeigels," Heidelberg. 1820. 'Joh. Muller, " I'ber dm 

 Bau der Echiuodcrmen," Abh. der Berl. Akad, 1853. Joh. Miiller. " Sieben 

 Abhaiidlimgen liber die Larven mid die Eiitwickelung der Echiuodermen." Abh. 

 der Berl. Akad, 184(i, 1848, 18 ii), 1850. 1851, 1852, 1854. A. Agassiz, " Embryo- 

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

 " Studien liber die Entwickclungsgeschichte der Echinodermeii mid Nemer- 

 tinen," St. Petersburg, 186U. if. Ludwig. " Morphologische Studien an 

 Echiuodermen," Leipzig 1877 and 1878. 



