ENTOZOA. 181 



For the arrangement of the numerous species of this genus, RUDOLPHI 

 availed himself also of the character of the booklets on the head, and 

 distinguished inermes and armatce. But since this character is inconstant, 

 and many of the inermes of RUDOLPHI have booklets in the younger period 

 of their life, it cannot be recommended for this purpose. Among the 

 species occurring in our domestic animals Tcenia plicata RUD., Tcenia 

 magna ABILDG., Zool. dan. Tab. 1 10, fig. i, BREMSER, Icon. Helm. Tab. xv. 

 fig. i, deserves to be recorded for the great size of its tetragonal head, which 

 surpasses that of all other species. It lives in the small intestine of the 

 horse. 



Dithrydium RUD. Uncertain genus. Comp. RUDOLPHI Entozoor. 

 Synops. p. 559, VALENCIENNES Ann. des Sc. nat. 3e Se*rie, n. Zool. 

 1844, p. 248. [VoN SIEBOLD, ibid. Vol. xv. p. 201, says it is a larval 

 form of a Tcenia without joints and sexual organs.] 



[RUDOLPHI'S first family of Entozoa is not included in the 

 systematic arrangement of the Class in this edition of the Hand- 

 book, because it has been satisfactorily proved by YON SIEBOLD, 

 VAN BENEDEN, DUJAKDIN, BLANCHABD, &c., that it consists of 

 larval forms of Tcenice, usually encysted in situations unfitted for 

 their further development, and in which they become distended 

 with fluid. But from the great interest that attaches to them on 

 account of their occurrence in the human body as well as in that of 

 other vertebrates, we subjoin the description of them, with a 

 reference to the literature contained in the 2nd Edit, of VAN DEB 

 HOEVEN'S Handbook.] 



Cystica. Body depressed or roundish, terminating posteriorly in 

 a vesicle full of fluid and proper to individual entozoa, or common to 

 several. Sexual and digestive organs none. Head furnished with 

 a coronet of booklets and four suctorial oscules. 



Comp. on cystic worms, AD. TSCHUDI, Die Blasen-wurmer. Ein mono- 

 graphischer Versuch. Freiburg im Breisgau, 1837, 4-to. mit 2 Kupfert. 



Echinococcus RUD. Vesicle either single or enclosed in an ex- 

 ternal capsule formed by the organ in which it is contained. On 

 the interior surface are set many entozoa, extremely minute, resem- 

 bling a grain of sand, with body obovate. 



. Worms in this state have been ordinarily named Hydatids, a name 

 which has also been extended to the rest of the cystic worms 

 indiscriminately, as well as to serous vesicles, the consequence 

 of a morbid nutrition, that contain no intestinal worms. LAENNEC 



