228 NATURAL HISTORY OF SOME TUBE-FORMING ANNELIDS. 



supply of food than may pass a given point out in the open. Support may be found 

 for the latter suggestion in the great abundance of many species of sessile worms 

 and other forms to be found in the mud in narrow passages of shallow water, where, 

 during certain phases of the tide, the water passes through in great quantities and 

 at a considerable rate of speed. 



Amphitrite does not always live in a tube of mud and sand. At the north- 

 eastern point of Nova Scotia I found, just beneath the rubble stone of an exposed 

 beach, a few small specimens with a partially formed tube about them. These 

 small specimens, when taken to the laboratory, appeared to be quite active, and, 

 in some instances, very much more active than larger specimens obtained in the 

 vicinity of Wood's Hole, Mass., where all were large, and provided with complete 

 tubes. 



In order to study the special activities of Amphitrite to the best advantage, 

 and in as nearly their natural surroundings as possible, I collected fresh specimens 

 from time to time in such a way as not to injure them, or to separate them from the 

 tube. Taken to the laboratory with some of the native mud and sand, they were 

 placed in aquaria with running water under conditions nearly normal. 



As already stated, the specimens obtained at Wood's Hole were large. In col- 

 lecting these specimens, it sometimes happened that a few were brought to the labora- 

 tory without any part of the tube on the body. Invariably the naked specimens 

 failed to reconstruct even the beginning of a tube, but continued to carry out what 

 seemed to be the same activities which, in partially enveloped specimens, resulted 

 in the formation of a complete tube. The mud and sand collected during the normal 

 tube-forming activities were heaped up under the body until the animal in its con- 

 tortions moved from the place and collected a heap elsewhere. I have many times 

 observed the same helplessness in specimens that I had dug up on the beach, and 

 lost on account of the clouded condition of the water. On returning to the place 

 later in the day, I have found the animal active, and still entirely uncovered. 

 I have tried in the laboratory the effect of covering part of the body of the naked 

 animal with mud, but never succeeded in getting them to perfect, or to continue 

 the covering. The Nova Scotia specimens were much smaller than any I ever saw 

 on the New England coast, but the percentage of adults found was, presumably, 

 as great in one place as in the other. Hence, the first suggestion that would occur, 

 that the great facility the Nova Scotia specimens displayed in forming a new tube 

 in any condition, could be accounted for on the basis of an instinct recently acted 

 upon as in youth, will not serve as an explanation. There is, however, something 

 in the nature of the environment which may be suggestive of an explanation. The 



