ROTATORIA. 203 
[Dusarpin (Infus. p. 268, 1841) gave reasons for the exclusion of 
Cheetonotus and Ichthydiwm from the Rotatoria, and placed them 
provisionally in his order Infusoires symétriques. Afterwards 
C. Voer referred them to the Twrbellaria. ScHuirzE discovered in 
the sea-sand at Cuxhaven (1853) a new genus and species closely 
allied in anatomical structure to our Jchthydina, which he named 
Turbanella hyalina. Neither in Ichthydium nor Cheetonotus do the 
cilia form a true wheel-organ round the mouth capable of protrusion 
and retraction. In Ichthydiwm they are spread over the entire 
abdominal surface ; in Chatonotus over the whole of the anterior half 
of the abdomen, and at the margin of the posterior half form a band 
which surrounds the closely set, stiff hairs, which are much finer than 
the spines on the dorsal surface and directed backwards to cover the 
non-ciliated portion of the abdomen. ‘The tail is forked, but not 
jointed. The intestine is straight, the anal opening at the fork of 
the tail. Neither vessels, nerves, nor muscles can be seen, except 
that the esophagus is muscular. The sexual organs are situated 
between the intestinal canal and the integument of the back, the 
testes consisting of a loose cluster of vesicles in front of the ovary. 
Scuunrze concludes that the Jchthydina of EnRENBERG (exclusive of 
his genera Piygura and Glenophora which are true rotatories ) must 
be excluded from the Rotatoria, and that they belong more nearly 
to the Zurbellaria than to any other order of worms. There are 
however remarkable differences of structure between them and 
any family of Turbellaria. For in those Turbellaria which have a 
straight intestine with anal opening, the sexes are distinct ; whilst 
in those which are hermaphrodite the intestine has no anal opening. 
Scuu.rzeE contends however that in worms the characteristic derived 
from the form of the intestinal canal is of greater systematic value 
than that derived from the formation of the sexual organs: and 
recommends that the Ichthydina, limited as above, be placed pro- 
visionally amongst the Microstoma of the order Turbellaria, which 
will then require to be subdivided into the dicecious and the monce- 
cious (Ichthydina). See Scuunrzn in Mvetier’s Archiv. 1853. 
s. 241-253. Taf. v1.| 
B. Rotatory organ multilobed or parted (Hydatinwa EHRENB.) 
Otoglena Eurens. Maxille none. Ocellitorm points three, the 
middle one sessile, the two lateral pediculate. 
Enteroplea Eurens. Body oval, oblong, anteriorly truncate. 
} , ? g , 
Maxillxw none. Ocelliform poimts none. 
