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- 



--aii 



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



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



1, Diurella tigris Mullor; 2, Diurclla 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 Miiller; 

 9, Rattulus carinatus Lamarck; 10, Rattulus lophoessus 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 



