48 



CLASSIFICATION OF THE ANIMAL KINGDOM. 



Fig. 42. Morphology of Chastognatha. A, Sagitta tricuspidata, of the natural size : o, One 

 of the ovaries ; sp, Orifice of one of male organs of reproduction. B, Head of the same, 

 viewed from beneath and greatly enlarged, showing the horny, setiform jaws. (After Saville 

 Kent.) 



DIVISION III. AETHEOPODA. 



CLASS I.-CEUSTACEA. 



SUB-CLASS I. EPJZOA. 



ORDER I. ICHTHYOPHTHIRA. Lerncea, Achthcres, Tracheli- 

 astes (fig. 43), Diocus (fig. 43), Chondracanthus, 

 Nicothoe, Caligus. 



The Ichthyophthira do not form a natural division of the Cnistacea, but 

 may rather be more properly regarded as comprising types which are 

 fundamentally allied to the Copepods, but which have undergone degra- 

 dation in consequence of their parasitic mode of life. 



(Nordmann, Neue Beitrage zur Kenntniss parasitischen Copepoden, Bull, 

 de la Soc. des nat. de Moscou, 1864 ; Glaus, Seobachtungen -fiber Lernce- 

 ocera, Peniculm, imd Lerncea, Marburg, 1868 ; Glaus, Ueber den Ban und 

 die Entwidcelung von Aclitheres percarum, Zeitschr. fiir Wiss. Zool., 1861.) 



OHDER II. EHIZOCEPHALA. Saccnlina, Pdtogastcr, Lerncco- 

 diseus. 



(Fr. Miiller, Die Rhizoceplialen, Archiv fiir Naturg., 1874.) 



