THE ROMANCE OF NATURAL HISTORY. 



pig-like plumpness. And when he swims away 

 and gives a fair view of his back to us, we notice 

 the evolution of a pair of hemispherical swellings, 

 one on each side of the broad head, and which are 

 evidently connected with his locomotion. The 

 whole front is clothed with vibrating cilia, but 

 they are more developed on these organs, which 

 are only pushed out at the will of the little ani- 

 mal, when they form strong vortical currents. 



In another part of the bunch of leaves possibly 

 a group of Salpinx may be feeding equally busily. 

 These are something like the former, but their 

 bodies are inclosed in a sort of shell or transpar- 

 ent case, much arched along the back, nearly 

 straight along the belly, and hollowed out at 

 each extremity. This shell is a very beautiful 

 object, when we meet with it, as we often do, 

 completely cleaned of the softer parts, the animal 

 having died. It is hard, perfectly transparent, but 

 marked all over with minute pits. It is closed on 

 all sides, except before and behind, where, as I 

 have said, it is cut away, as it were, for the 

 egress of the head, and the forked foot : along the 

 back it rises into two tall, longitudinal, sharp 

 ridges with a deep furrow between them, and the 

 appearance of this double ridge, from the perfect 

 transparency of the material, has a curious effect 

 as the animal moves about. Both before and be- 

 hind, the ridges run out into projecting points, 

 those of the front arching over the head like curv- 

 ing horns. These little animals derive their nour- 

 ishment likewise from the soft vegetable tissues, 

 or the half-dissolved matter that accumulates on 

 the stems and leaves of the aquatic plants. On 

 this they feed greedily, and nearly the whole of 

 their time is spent in munching away this with 

 the mouth. To do this the foot, which consists of 

 100 



