234 NATURAL HISTORY OF SOME TUBE-FORMING ANNELIDS. 



body, and placed on that part of the tube where it is needed. If the object is too 

 heavy to be lifted from above, the animal crawls with its head beneath the mass, 

 and, grasping the object with palps and cirri, and extending the mandibles, it lifts 

 and carries the object to its proper place. If, again, the object is too heavy to be 

 carried by grasping from above, or not convenient to crawl under, Diopatra pushes 

 the object into position by extending the palps over the edge, as I have observed it 

 do with heavy pieces of broken glass. After a few pieces have been placed in posi- 

 tion the animal ceases to collect materials, and begins the process of gluing together 

 that already collected. This is done by repeatedly pushing outward, and, as it does so, 

 rubbing the ventral glands, which begin at the sixth trunk somite, forcibly against the 

 inner surface of the tube. The process is continued, if not interrupted, until the new part 

 of the tube is glued all round. The animal may then, or after adding more material, 

 double on itself, the dorsal surface always inward (protecting the gills), and build 

 and glue at the other end. I have tried, while the animal was energetically engaged 

 in gluing, to see if that function could be interrupted. I held before it a small piece 

 of shell so as to touch the cirri. At once gluing ceased, and the piece was grasped 

 and placed in position. The annelid then continued for some time collecting more 

 material. At no time was there evidence of a choice between kinds of objects for 

 tube construction, pebbles, bits of shell, and even glass, being taken indiscriminately. 



During the process of collecting material the animal frequently cleans its cephalic 

 cirri by bending them down one at a time and catching them between the dorsal and 

 ventral rami of the second or third parapodium. Even the mid-dorsal tentacle is 

 cleaned in this way. The setse are the actual cleaners. 



In a small aquarium where there is plenty of waste for building, but no mud to 

 bore into, Diopatra will construct within an hour or less a serviceable tube to cover 

 the entire body, or that part of the anterior region remaining after the animal has 

 broken itself, as it sometimes does. The length of tube thus completed is at least 

 three inches. One Diopatra on which I experimented reformed its tube three times 

 within two days, but the third time it appeared to be considerably exhausted. Never- 

 theless, the animal lived without food two weeks longer. Specimens placed in a vessel 

 containing mud, sand, and waste, such as pebbles and pieces of shell, will first bore 

 into the mud and along near the surface. This operation is kept up for some time. 

 Then the animal begins to collect waste for protecting the portion above ground. 

 No pebbles were found in these aquarium-built tubes below the surface. The reason 

 is plain the pieces could not be put in position conveniently. 



In only two instances were perfect Diopatra found, and these, on being forced 

 from their tubes, constricted at about the middle until the animals had broken them- 



