ROTATORIES. 171 



fully illustrated by Mr. P. H. Gosse in the Microscopical Society's 

 Transactions . 



Mr. Gosse states, that his specimens were found in a jar of water 

 obtained in the autumn from a pond near Walthamstow, the jar having 

 stood in his study-window through the winter ; and from a swarm in 

 the succeeding February he selected one the 70th of an inch in length 

 when extended, but its contractions and elongations rendered its size 

 variable. 



" Its form, viewed dorsally, is somewhat cylindrical, but it frequently 

 becomes pyriform by the repletion of the abdominal viscera. Viewed 

 laterally, the back is arched, gibbous posteriorly, with the head some- 

 what obliquely truncate, the belly nearly straight. The posterior ex- 

 tremity is produced into a retractile foot, terminating in two pointed 

 toes ; this, both in function and structure, is certainly analogous to a 

 limb, and must not be mistaken for the tail, which is a minute pro- 

 jection higher up the body. When not swimming or rotating, the 

 head assumes a rounded outline, displaying through the transparent 

 integument an oval mark on each side, within which a tremulous motion 

 is perceived ; but at the pleasure of the animal a semi-globular lobe is 

 suddenly projected from each of these spots by evolution of the integu- 

 ment. These projections have suggested the trivial name of aurita. 

 Each lobe is crowned with a wheel of cilia, the rapid rotation of whose 

 waves forms the principal source of swift progression in swimming. 

 The protrusions of these lobes are evidently eversions of the skin, ordi- 

 narily concealed in two lateral cavities. They may be protruded by 

 pressure, and are then seen to be covered with long but firm and close- 

 set cilia, which are bent backward, and move more languidly, as death 

 approaches. The whole front is also fringed with short vibratile cilia, 

 which extend all along the face, as far as the constriction of the neck. 

 The whole body is clear and nearly colourless ; but its transparency is 

 much hindered by the net-work of dim lines and corrugations that are 

 every where seen, particularly all about the head." 



Mr. Gosse, on puttiijg carmine into the water, saw the jaws work- 

 ing slightly, the points opening a little way, and then closing; the rods 

 of the hammers were drawn towards the bottom for opening, and up- 

 wards for closing. A little mass of pigment was soon accumulated 

 beneath the tips of the jaws, which spread itself over a rounded surface, 

 but did not pass farther j nor did an atom at this time go into the 

 stomach. 



After entering into further minute details of the little animal, he ob- 

 serves : " They possess organs that many others do not, and want some 



