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 Cesium, 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. Ct/dij)pe Iiormi2>hora Ggbr. = 

 Ilormipnora plumoaa Ag., Mediterranean. Esclischoltzia cordata Koll., 

 Mediterranean. 



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

 sagittal plane. Two tentacles. Vexillum paralleluin Fol., Canary Isles. 

 Cestum Veneris Less., Venus' Girdle, Mediterranean. 



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

 lobes near the mouth, and has relatively small tentacles. Eurhampliaca vc.ril- 

 ligera Ggbr., Mediterranean and Atlantic Ocean. Cldnja papillosa, M. Edw. 

 (Alcinde papillosa Delle Ch. = Xcapolitana Less.), Mediterranean. 



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

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

 Beroe ForsJialii M. Edw. (albcsccns and rtifescens Forsk.), Idyiopsis Clarlii 

 Ag., Pandora Flcmmingii, Esch. 



CHAPTER VIII. 



ECIIINODERMATA.* 



Animals with a radial, usually pentameroiis arrangement. TJiey 

 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 Medusse and Polyps. It is only 

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

 Echinoderms from the Coalenterates. 



The organization of the Echinoderms does in fact appear so different 

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

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



* Fr. Tiedemann, " Anatomie der Rohrcnholothurie, des pomeranzfarbeuen 

 Scesterncs und des Stcin-Seeigels," Heidelberg, 1820. Joh. Milllcr, " Uher den 

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

 Abhandlungen iibcr die Larven und die Entwickelung der Echinodermcn." Abh. 

 der Berl. Akad, 1846, 1848, 18)9, 1850, 1851, 1852, 1854. A. Aeassiz, " Embryo- 

 logy of the Starfish." Contributions, etc.. YoL, V. 18G4. E. Metschnikoff, 

 " Studien iiber die Entwickelungsgeschichte der Echinodc-rmon und Nerner- 

 tinen," St. Petersburg, 1-<C9. H. Ludwig, " Morpholoirische Studien an 

 Echinodermen," Leipzig 1877 and 1878. 



