182 
Becent Progress in our Knowledge of 
(1) the cuticle layer, (2) the cilia layer, (3) the myophan layer, 
(4) the trichocyst layer. 
The cuticle is nothing but a lifeless exudation from the surface. 
In the majority of Ciliata there is no true cuticle, and in those 
which possess it, it presents itself under various forms, as seen in 
the thin, chitine-like, hyaline homogeneous pellicle of Paramoecium 
and Trichodina, the outer elastic layer of the stem of the Yorti- 
cellinse, the protective sheath of Yaginicola, the chitine-like cases of 
the Tintinnodese and Codonellidae, the beautiful lattice-like silicious 
shells of the Dictyocystidse (Fig. 4), and many other shells, cases, 
and shield-like protections.* 
The cilia layer occurs in all Ciliata ; it lies immediately beneath 
the cuticle where this is present, and the whole of the cilia and 
other mobile appendages are its immediate extensions. These must 
therefore perforate the cuticle or its modifications when such pro- 
tective coverings exist. 
The myophan layer is identical with that which most authors 
describe as a true muscular layer. It has been demonstrated in 
most of the Ciliata. It appears as a system of regular parallel fine 
striae in the walls of the body, and in the Vorticellidse occupies also 
the axis of the stem, where it forms the characteristic "stem- 
muscle " of these animals. There can be no doubt that these striae 
represent contractile fibrils, which, by their contraction, effect the 
various form changes of the animal. They are thus physiologically 
analogous to muscles. From a morphological point of view, how- 
* In the same number of the ' Zeitschrift,' Haeckel (" Ueber einige nene 
pelagische Infusorien ") describes some highly interesting Infusoria which spend 
their lives in the open sea and are distinguished by the possession of variously 
formed shells. His attention was first directed to them by finding their elegant 
empty shells in the extra-capsular sarcode of Eadiolarise. These pelagic Infusoria 
appear to belong to two different groups, which stand nearest to the Tintin- 
nodege of Claparede and Lachmann. He designates them as Dictyocystidce and 
CodonellidcB. 
The family of the Dictyocystidse is based on Ehrenberg's Dictyocysta, and is 
characterized by the possession of a silicious perforated lattice-like shell so closely 
resembling that of many Kadiolarise, that Haeckel at first mistook it for the shell 
of one of these. The shell is in all the species bell-shaped or helmet-shaped, and 
the body of the animal, which is fixed to the fundus of the bell, and can be 
projected far beyond its margin, has a wide funnel-shaped peristome on whose 
edge are two concentric wreaths of strong cilia. He describes four species, dis- 
tinguishing them by characters derived from their silicious latticed shell. 
The family of the Oodonellidse, based on the genus CodoneUa, Haeckel, is also 
provided with a bell-shaped case, but this, instead of being formed of a silicious 
lattice work, consists of a cliitine-like organic membrane, through which silicious 
particles are scattered. The family is, however, chiefly characterized by the 
poculiar form of its peristome. This is funnel-shaped and provided on its margin 
witii a thin collar-like expansion. The free edge of tliis collar is serrated, and 
each tootli carries a stalked lobe of a piriform shape, regarded by Haeckel as 
probably an organ of touch. At some distance behind the circle of piriform lobes 
is situated a ring of long, strong, whip-lilte cilia, which form powerful swimming 
organs. The three species described are distinguished by the form of their 
chitinouB cases. 
