SOME AQUATIC WORMS, ETC. 



183 



rather longer. It is movable and exceedingly flexible, 

 the Dasydytes continually bending from side to side in 

 search of food, or upward and downward. The ani- 

 mal occasionally has the habit of turn- 

 ing somersaults, accomplishing this 

 feat by flexing the neck under the ven- 

 tral surface and throwing the body 

 over forward. From each side of 

 what may perhaps be called the shoul- 

 ders, arise from four to six large, 

 coarse bristles, each as long as the en- 

 tire body. These sets of bristles cross 

 each other obliquely above the back, 

 and project beyond the rounded pos- 

 terior extremity. Without these the 

 dorsal surface would be naked, ex- 

 cept for the presence of two, fine, 

 almost vertical tactile hairs, each of 

 which arises from a small papilla near 

 each postero-lateral border. 



The ventral surface is not easily seen, as the animal 

 usually keeps obstinately directed downward. But the 

 ventral cilia are essentially similar to those of Chgeto- 

 notus and arranged in two lateral, longitudinal bands. 

 But near the center of this aspect originate four strong 

 coarse bristles, or setas, two long and much exceeding 

 in length that of the whole body, and two shorter, the 

 four projecting beyond the posterior border. These 

 are springing sets by which the Dasydytes makes those 

 surprising leaps which suggested its specific name of 

 saltitans, or leaping, often jumping, and always unex- 

 pectedly, to a distance. sometimes exceeding twice its 

 own length. This seems to be great but in reality it 



Fig. 136. — Dasydytes 

 saltitans. 



