198 CLASS VI. 
to the mother and carried about by her (Brachionus, &c.); and thus, in the cold season 
of the year, these animals are oviparous. 
Besides the male of Notommata anglica, discovered by BRIGHTWELL, that of NV. 
Sicboldii has been observed by Leyp1G, who further gives reasons for believing that 
Enteroplea hydatina Eur. is the male of Hydatina senta, Notommata granularis the 
male of Notom. Brachionus, and Diglena granularis the male of Dig. catellina. 
Gosss also has ascertained that the sexes are distinct in many others’, The males 
are less than the females, and also differ in form in most cases. The dioecious character 
of the class may thus be considered to be established. 
The generative organs of the males consist of a white and round 
bladder or testis, filled with spermatozoa, and an efferent duct 
(penis DALRYMPLE) ciliated in the interior, which opens close to 
the outlet of the respiratory vesicle. All the males observed are 
entirely destitute of digestive tract; they possess the respiratory 
organs of their species, whose function seems to suffice for the 
maintenance of their short life, employed exclusively in impreg- 
nating the females. ] 
The nervous system has been discovered by HHRENBERG in 
different genera, and he described, as central portion, different ganglia 
(ganglia cephalica seu cerebralia), situated close to the wheel-organ, 
from which distinct nerves arise. In Hydatina senta, according to 
the investigations of the same observer, two threads also arise from 
them that run downwards on the abdominal surface, and unite to form 
a ganglion from which a single nervous string with many small 
ganglia or swellings arise®. As organs of sense, in most of them red 
eye-spots (generally two, sometimes one or three, seldom more than 
four) have been perceived; sometimes these exist in young individuals 
alone, and disappear on full growth, as in the genus Foscularia. 
Besides the muscles of the special parts, there are found in many species thin 
bundles of muscles running longitudinally, one on the dorsal surface, one on the 
abdominal surface, and two lateral. 
With respect to the geographic distribution of Wheel-animalcules nothing deter- 
minate can yet be specified. Only do we know, from the observations and notices of 
EHRENBERG, that, besides Europe, they are found in northern and western Asia, in 
the north of Africa and in North America, Beyond doubt they occur in all quarters 
of the world. The physiological peculiarity of life suspended for a length of time, to 
be again awakened by the vital stimulus of fluid, has given a special celebrity to these 
animals. On this subject we refer to what will be offered below when we notice 
Rotifer vulgaris, in which this phenomenon has been chiefly observed. 
1 [GossE On the dioecious charact. of the Rotifera, Proceedings of the Royal Soc. 
Vol. vill. pp. 66, 68.] 
2 Die Infusionsthierchen, s. 416. Somewhat differently ordered is the nervous 
system in Notommata (s. 425) and in Diglena (s. 443), but in all there lies a principal 
mass, as the collection of nervous ganglia, on the dorsal surface of the anterior 
extremity of the body. 
