}2 DR. R. E. GRANT ON THE NERVOUS SYSTEM OF BEROE PILEUS. 
regular and rapid vibrations of these very minute organs in the lowest forms of animal 
organization, depend on volition directed at once to thousands of millions of muscles. 
When the tentaculum of a Flustra is cut off from the polypus, I have observed it swim 
like a straight worm, or a Vorticella, through the water by the action of the cilia still 
continuing ; and it was observed by Fabricius, that when the Beroé is broken to pieces 
these continue to live, and to swim about by the action of the cilia still kept up. The 
tubular feet which project from the ambulacra of the Asterias, rise and sink in constant 
succession by the entrance and exit of water sent into them by vessels destined for that 
office. The same mechanism is observed in Echinus and in Holothuria, (the forms of 
which, as well as the arrangement of the feet, closely resemble those of the Beroé,) and 
the tubular tentacula of Actinia rise by the injection of water into them from their base. 
It appears therefore highly probable that the motions of the cilia of the Beroé are inti- 
mately connected with the streams passing along the bands; and should the rapid 
vibrations of these singular organs in the lowest animals depend on the undulations of 
water conveyed through elastic tubes along their bases, one of the most remarkable 
phenomena of animal motion, though one of the most. frequent, will lose much of its 
present marvellous character, and prove another instance of the striking similarity of 
the phenomena of the simplest organic beings to those which occur in the inorganic 
world. 
PLATE II. 
Fig. 1. Beror Pitevs, Lam. (twice the natural size). 
