ENTOZOA. 181 
For the arrangement of the numerous species of this genus, RUDOLPHI 
availed himself also of the character of the hooklets on the head, and 
distinguished inermes and armate. But since this character is inconstant, 
and many of the énermes of RuDOLPHI have hooklets in the younger period 
of their life, it cannot be recommended for this purpose. Among the 
Species occurring in our domestic animals Tenia plicata Ruv., Tenia 
magna ABILDG., Zool. dan. Tab. 110, fig. 1, BREMSER, Jcon. Helm. Tab. xv. 
fig. 1, 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 Rup. Uncertain genus. Comp. Rupotpui Lntozoor. 
Synops. p. 559, VALENCIENNES Ann. des Sc. nat. 3e Série, 1. Zool. 
1844, p. 248. [Von Siepoxp, ibid. Vol. xv. p. 201, says it is a larval 
form of a Z’enia without joints and sexual organs. | 
[Rupotrurs first family of Zntozoa is not included in the 
systematic arrangement of the Class in this edition of the Hand- 
book, because it has been satisfactorily proved by Von Srepoxp, 
Van Benepen, Dusarpin, BLancHarp, &c., that it consists of 
larval forms of Zenie, 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 cf 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 DER 
Horven’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 hooklets and four suctorial oscules. 
Comp. on cystic worms, AD, Tscuup1, Die Blasen-wiirmer. Ein mono- 
graphischer Versuch. Freiburg im Breisgau, 1837, 4to. mit 2 Kupfert. 
Echinococcus Rup. 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. LAENNEG 
