AND ITS BIOLOGICAL SIGNIFICANCE; 



323 



The species of this group are usually of small size, and the body is covered with 

 a somewhat stiff shell, or lorica, formed by the hardened cuticula. At the anterior 

 end is a ciliated area or corona, by means of which the animal swims; this may be 

 retracted within the lorica. The body is usually elongated and nearly oval or cylin- 



— ai.1. 



Fig. E. — Dorsal views of a number of species of Rattulidse (original). Abbreviations: at.d., dorsal antenna; at.l., 



lateral antenna; ence., brain; pd., foot. 

 1, Diurella tigris Muller; 2, Diurella stylata Eyferth; 3, Rattulus scipio Gosse; 4, Diurella insignis Herrick; 

 5, Diurella porcellus Gosse; 6, Rattulus elongatus Gosse; 7, Rattulus bicristatus Gosse; 8, Rattulus rattus Muller; 

 9, Rattulus carinatus Lamarck; 10, Rattulus]lopnoessus Gosse; 11, Rattulus gracilis Tessin; 12, Rattulus latus 

 Jennings! 



drical in form. At the posterior end is a small separate joint, known as the foot. 

 To the foot are attached one or two bristle-like structures which are usually called the 

 toes. All these features will be appreciated by an examination of Figure E. The 



