3408 THE WORM-LIKE ANIMALS 



polychsetous annelids, and we may take as our first example the sandworm (Areni- 

 cola piscatorum), represented of the natural size in D of the illustration. This 

 worm reaches a length of about eight inches. Individuals vary, however, much in 

 color, according to the nature of the mud or sand in which they are found; those 

 living in clean sand being of a light tint, whereas black specimens frequent slimy 

 sand, strongly impregnated with decaying organic matter. The segments of the 

 body are not all alike; those at the front end being furnished with a few small, 

 widely-separated tufts of bristles arranged in pairs; then follows a series in which 

 the clusters of bristles are large, bush-like, and close together; while the end of the 

 body is cylindrical and without bristles and parapodia. The goblet-shaped organ, 

 shown in the illustration, projecting from the head is the protruded proboscis. This 

 worm, which is found on all the coasts of Europe, is used by fishermen as bait. At 

 low water, on some sandy shores, it may be found in vast numbers. 



In the family Clymenida, to which belongs the worm known as Arenia fragilis, 

 the body is only divisible into two regions. The fore part, which is of a dirty red 

 tint, alters its shape greatly owing to the retraction and extension of its segments; 



Arenia fragilis (natural size). 



while the exceedingly long and slender hinder part is of a yellowish color. A re- 

 markable family is that of the Ch&topterid&t containing the genus Chcetopterus, of 

 which a specimen is represented of the natural size in the illustration on p. 3409. 

 The head is funnel shaped, with an indentation on its upper side, and from this 

 springs a pair of feelers. The body is marked out into three regions; the most strik- 

 ing being the formation of the five segments which compose the middle region of 

 the body. From the first segment of this area the parapodia stand out like a pair 

 of flat feelers, while the lower branches of these feet are spread like a ruff over the 

 abdominal region. The upper branches of the parapodia of the second segment 

 unite with those of the first to form a dorsal crest, and between these and the lower 

 branches the skin is much swollen and of a violet color; the following three seg- 

 ments are swollen and have relatively short parapodia. Species of these worms are 

 found on the coasts of Normandy and in the Mediterranean. Like many other 

 marine animals, this worm is phosphorescent, the phosphoric matter spreading like 

 a cloud in the water. 



In the next group the gills are in the form of small trees or branches of threads 

 attached to the end of the head; while the mouth is unprovided with either teeth or 



