10 DR. R. E. GRANT ON THE NERVOUS SYSTEM OF BEROE PILEUS, 
tapering to a very fine extremity. Along their whole course they present minute equi- 
distant filaments, extending from their lower margin, which coil themselves up in a spiral 
manner, and adhere close to the tentacula when they are about to be withdrawn into 
their sheaths or tubes. These tubes have a sigmoid form, and are shut and somewhat 
dilated at their upper extremity. The tentacula seem to be spirally twisted in them when 
withdrawn. The tentacula are often thrown out from the tubes to their full extent by 
one impulse, and the slow uncoiling of the slender serpentine filaments from their margin 
is then very beautiful ; when coiled up, they appeared like very minute tubercles along 
the side of the tentaculum. The animal often poised its body in the water, without 
moving the cilia, by extending these minute filaments to the bottom of the vessel. I 
observed that both the Beroé and the Equoree were inconvenienced by each other’s 
presence, and less free in the extension of their delicate tentacula, until they were put 
into separate vessels. 
At a short distance above the mouth I could perceive a double transverse filament of 
a milky white colour, like that of the abdominal nerves of the Pectinaria and other 
transparent animals, which formed a continuous circle round the body. In the middle 
of the space, however, between each of the bands of cilia, these cords presented a small 
knot or ganglion, so that there were eight ganglia in the course of this ring. From each 
of these ganglia two nerves on each side passed to the adjoining band, and a larger 
filament from each ganglion could be traced upwards in the middle of the transparent 
space between the bands to beyond the middle of the body. In the course of these 
longitudinal middle filaments two or three smaller ganglia could be observed, from 
which filaments were directed inwards to the viscera. These filaments and ganglia were 
situated near the surface of the body ; and from their general appearance and their mode 
of distribution, there can be little doubt that they constitute the nervous system of this 
animal. ‘This arrangement of the nervous system is analogous to that of Holothuria 
and Asterias among the Echinoderma, in the circular disposition of the central filaments 
and ganglia, and in the regular radiation of nerves from that circle. All the movements 
of the Beroé are of a lively character ; its tentacula and the lips of the mouth appear to 
be exquisitely sensible ; the animal frequently contracts its body longitudinally or trans- 
versely by a sudden impulse, and when it is at rest the slightest agitation of the vessel 
containing it, causes it to commence instantaneously the rapid vibration of its cilia. 
The Rotiferous animalcules are found to possess a complex nervous system, consisting 
of cerebral and cesophageal ganglia and longitudinal nervous filaments, and even the 
Polygastric animalcules possess organs of vision. I am inclined therefore to believe, 
that although nerves have not hitherto been shown in the Acalepha, they will be found 
even in the simpler forms of Meduse, which I have shown elsewhere to be affected by 
light, as well as Actinie, Hydre, and Furcocerce. 
The cilia of this Beroé are the largest I have yet met with in any animal. These 
singular minute vibratile organs perform important functions in the simpler forms of 
