I. AMPHITRITE ORNATA VERRILL. 



It is not my purpose to present an exhaustive account of the habits of tube- 

 forming annelids, but rather to put into concise form a description of some of their 

 more or less well-known activities, with occasional suggestions as to the significance 

 of certain details. 



It appears that the most of what is known about the manner of living of annelids 

 has been learned by those whose chief interest lay in economic relations, taxonomy, 

 or embryology, rather than in the consideration of minute adaptations of structure 

 to function. It seems to me the latter point of view is likely to be the most fruitful 

 one in taking up the investigation of the habits of animals. 



Amphitrite forms a thick-walled, U-shaped tube of mud and sand, colored brown 

 on the inside by mucus from glands. The exact location of the tube in the submerged 

 mud-flat at low water may be known by characteristic miniature hills, not more than 

 one inch high, with a slight depression at the center. Two or three tentacles of the 

 animal may always be seen extending from the crater of the little hill, down its sides, 

 and over the level to a distance of three to five inches. The tentacles are covered 

 with fine particles of sand, and, ordinarily, would be almost indistinguishable, if it 

 were not for their constant, slight movement. 



As a rule, Amphitrite has its tube in a partially clear space in the eel-grass area, 

 or along the margin of it. It is not always possible to demonstrate from the surface 

 of the mud that both arms of the U-tube come to the free water, because the tide and 

 the activities of other animals may result in the temporary disappearance of such 

 evidence. However it is easy to follow the tube by digging and thus to show that 

 it is always shaped like the letter U. In one stretch of beach examined, where these 

 annelids were large and fairly numerous, the greatest number appeared to be dis- 

 tributed about a few large boulders, the lower portions of which were always under 

 water. There were probably two factors influencing this local distribution. The 

 first of these was the firmness of the mud about the boulders, for the coarse gravel 

 caught in the swirl of the tides finds lodgment near the boulders, rendering more 

 firm the sand and mud in that region. Amphitrite, being somewhat helpless, needs 

 a firm enveloping mud. The second factor is connected with the first. While the 

 tide flows more swiftly about the boulders, it brings to the animals there a greater 



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