120 LIFE BY THE SEASHORE. 



film. It is not uncommon under stones on the shore, but 

 requires a trained eye to distinguish it. When turning over 

 stones in search of worms it may be that on the upturned 

 surface, among sponges, tunicates, and what not, you are 

 struck by a delicate film which glides over all obstructions 

 with the smooth movement of a drop of water over a 

 polished surface. Slip a blunt knife carefully beneath it, 

 and drop it into your collecting-bottle. You will notice that 

 it swims through the water by vigorous flaps of the body, 

 with a motion which has been compared to that of a skate. 

 As it settles again on the edge of the bottle, notice with a 

 lens that the mouth is on the mid-ventral surface, and that 

 the greatly branched alimentary canal is visible, ramifying 

 throughout the greater part of the body. There is no 

 distinction in appearance between anterior and posterior 

 end, except that the anterior is furnished with little black 

 specks the eyes. The little creature will live for a time 

 in captivity, and the grace of its movements makes it a 

 charming inhabitant of the aquarium. The details of 

 structure are too difficult for our purpose, but the animal 

 is worth mention, if only on psychological grounds. It is 

 far from uncommon, and yet many diligent shore hunters 

 never find it at all. If, therefore, you find no difficulty in 

 obtaining specimens, you may flatter yourself that you have 

 acquired the first essential of a shore naturalist quick 

 observation. 



Sometimes associated with Turbellaria are another set of 

 flat worms, the Nemerteans, or ribbon-worms. Many of 

 these occur on the shore, but we shall limit ourselves to 

 two the pink ribbon-worm (Amphiporus lactifloreus) and 

 the great sea-snake (Linens marinus). Under stones at all 

 parts of the shore one may find the pink ribbon-worm, 

 living in a slight tube made of sand cemented together by 

 mucus. It is one to two inches in length, but is extra- 

 ordinarily contractile. From a bristle-worm it differs 

 markedly in the absence of bristles or any sign of segmenta- 

 tion. In the head region the eyes will be noticed, and also 

 two slits at either side of the head. These are eminently 

 characteristic of the ribbon-worms in general. So also is 

 the so-called proboscis, a slender thread which the worm 

 may be seen to protrude from a pore above the mouth, 



