

NATURAL HISTORY. 



One more parasite must be mentioned, — the spine-headed worm 



nnorhynchus), — which is very abundant in pigs. It and its numer- 



brothers belonging to the same genus are raised to a group equiva- 



i n r ank to the flal worms and the thread- worms, under the name 



nthocephali, — a term which is merely a translation of the common 



name into Greek. The history of these parasites is as yet 



almost unknown, but their anatomy has been carefully studied. 



We only need say that they have neither mouth nor digestive 



tract, but, like the tape-worms, obtain their nourishment by 



absorbing it through the skin. 



While we know but little of the place where the spine-headed 

 worms belong, we know but little more concerning the rela- 

 tionships of another form, known as Sagitta, which lives a 

 free life in the ocean. The name Sagitta means an arrow, 

 and describes well the shape of these animals. They are an 

 inch or two in length, nearly transparent, and furnished with 

 two bunches of bristle-like jaws, one on either side of the 

 mouth. On either side of the body and on the tail is a fold 

 which frequently becomes broken up into separate fins. Sagitta 

 swims freely at the surface of the sea, and the surface-net of 

 the naturalist often takes it in large numbers. 



The student of natural history at the sea-shore soon learns 

 that the sand and mud between tides are full of life, and 'worm- 

 digging' plays an important part in his investigations. Occa- 

 sionally the spade will expose to view a portion of an enormous, 

 tlit. dirty white or flesh-colored worm. He seizes it, when, with 

 almost lightning-like rapidity, a slender, fleshy thread is thrown 

 I from the head of the worm; round and round his hand it 

 goes, stretching out to an incredible length, running up his arm, 

 ami no matter how strong his nerves, and how often he has had 

 the experience, he cannot help being startled at the occurrence, 

 lie has found a Nemertean worm, and this long, binding thread 

 ix its proboscis, with which it captures its food. It cannot 

 cause the slightesi harm to man, but it never fails to excite 

 feelings of disgust. This form, whose habit we have thus 

 uded to, is one of the largest of the group. It bears the name Meck- 

 ingens, ami when extended to its fullest length, the worm, without 

 • proboscis, may reach the length of fifteen or even twenty feet. Others 

 tierteana are much smaller, and are among the most common of 



Some are white, others blood-colored or green, and still 

 nearh black. 









