WHEEL-BEAKERS. 239 



delicate little "Whiptail, which I am going to make the 

 subject of our evening's study. It is inclosed in a glassy- 

 shell (lorica) of a long oval form, from which rises on the 

 front half of the back a thin ridge, which in the middle 

 has a height nearly equal to half the diameter of the body, 

 but tapers off at each end. Its base is corrugated with 

 wrinkles. This is not set on symmetrically, but leans over 

 considerably to the right side. Its basal portion is hollow, 

 and is continuous with the general cavity of the shell, for 

 we sometimes see portions of the viscera in its interior. 



WHIPTAIL. 



The head of the animal is rounded, and divided into 

 several blunt eminences or lobes, which are set with cilia; 

 these rotate constantly, but irregularly and feebly, and do 

 not make manifest wheels, as Brachionus does. A small 

 antenna projects from the back of the head, capable of 

 being erected or inclined. A long brain descends along 

 the base of the ridge, carrying a bright and rather large 

 crimson eye set like a wart on its interior angle. 



Instead of the flexible and contractile foot of Brachi- 

 onus, the Whiptail has a single horny spine of great 

 slenderness, and exceeding in length" the whole body. 

 This spine probably represents not the foot, but one of 

 the toes at the end of the foot. For it is attached to a 

 very short foot, in the midst of two or three bract-like 

 spines, one of which, longer than the rest, and distinctly 

 movable, probably represents the other toe undeveloped. 

 The long spine is set-on by a proper joint, a globose bulb 

 being inserted into a socket, which allows it free motion 

 in all directions except backward. The socket itself is 

 contained in a second joint, the basal part of which is 



