398 DESCRIPTION OF [Hot at or ia. 



shorten itself, transverse folds or joints are observable, 

 which do not appear to be confined in number or situation ; 

 the integuments, when a joint is produced, are drawn 

 within the parts above, and slide out like the tubes of a 

 telescope, when the joints disappear. It is this power that 

 enables it to assume the form of a sphere, the head and 

 tail being drawn within the body." Anteriorly it has a 

 proboscis-like process, with a ciliated extremity, and a soft 

 hook ; near its end are two dark red points. The body 

 terminates in a moderately-long tail-like foot, having six 

 processes, disposed in pairs; two wreaths of cilii (the wheels), 

 voluntarily moveable, are placed upon short thick arms 

 (pedicled), which can be drawn in and out at pleasure ; 

 these wreaths serve for swimming and purveying, the food 

 approaching it by the currents produced in the water by 

 the cilii. On the dorsal surface is a styliform horn (Spe- 

 culum colare, M.) destitute of cilii at its end. During 

 vibration the neck has a circular fold, appearing like lateral 

 styles. Four muscles, two anterior and two posterior, 

 longitudinal, are seen; laterally, also, two club-shaped, for 

 moving the foot, and two belonging to the rotatory organ. 

 Sometimes, says Dr. Ehrenberg, four anteriorly longitu- 

 dinal muscles, and a dorsal and ventral one, appear to be 

 present. It has two kinds of locomotion, one by alternately 

 attaching the mouth and foot, and, as it were, stepping 

 along ; the other by swimming, from the action of the rota- 

 tory apparatus. If the creature attaches itself by the foot, 

 and the rotatory apparatus is in motion, a strong current 

 or vortex is produced on each side the wheels, resembling 

 two spirals in the water, which bring the nutritive particles 

 to the mouth, from which some are chosen, and the rest 



