$ 121. THE TURBELLARIA. 133 
Genera: Polycelis, Monocelis, Planaria, Leptoplana, Eurylepta, Planoce- 
ra, Thysanozoon. 
BIBLIOGRAPHY, 
a Ueber Planarien, in the Noy. Act. Acad. Leop. XIII. 1826, 
p. 691. 
Dugés. Recherches sur l’organisation et les moeurs des Planariées, in 
the Ann. d, Sc. Nat. XV. 1828, p. 139; and XXI. 1880, p. 72. See 
Isis 1830, p. 169, or Froriep’s, Not. 1829, No. 501. 
Mertens. Ueber den Bau verschiedener in der See lebender Planarien, 
in the Mém. de l’Acad. de St. Petersbourg, 6°™* Sér. Tom. II. 1833, p. 1. 
aoe Phytozoa turbellaria, in the Symbolae physicae, Ser. I. 
31. : 
Focke. + Ueber Planaria Ehrenbergii. in the Ann. des Wiener Mus, I. 
Abth. 2, 1836, p. 193. 
F. F. Schulze. De Planariarum vivendi ratione et structura penitiori 
nonnulla. | Dissertatio. Berolini, 1836. 
A. S. Orsted. Entwurf einer systematischen Eintheilung und speciel- 
len Beschreibung der Plattwiirmer. Copenhagen, 1844. 
ADDITIONAL BIBLIOGRAPHY. 
Beside the writings referred to in my notes, see the following: 
; oe Die rhabdocoélen Strudelwiirmer des siissen Wassers. Jena, 
848. 
Neue Beitrage zur Naturgesch. der Wiirmer. Jena, 1848, Enrster 
Abschnitt, Turbellarien. 
Handbuch d. vergleich. Anatomie, 1849, p. 294. 
M. S. Schultze. Ueber die Microstomeen, eine Familie der Turbellarian, 
in Wiegmann’s Arch. 1849, p. 280, Taf. VI. 
Beitrage zur Naturgeschichte der Turbellarien. 1851.— Ep. 
CHAPTER I. 
CUTANEOUS SYSTEM, 
§ 121. 
The whole body of the Turbellaria is covered with ciliated epithelium, 
under which lies a loose cellular parenchyma. In this parenchyma, and 
directly beneath the epithelium, there are found, in many species, particu- 
lar cell-like bodies, which sometimes remind one of the nettling organs of 
certain zoophytes, and sometimes exactly resemble the prehensile organs 
12 
