1883.] NATURAL SCIENCES OF PHILADELPHIA. 205 



most tubicolous annelides. The simple tubes range from two to 

 four lines in length by the one-fifth to the one-fourth of a line in 

 width. 



3Ianayunkia is very sensitive, and on disturbance withdraws 

 deeply into its tube, so that half the length of the latter may be 

 removed before reaching the worm. The little creature clings 

 tightl}^ to the inside of its habitation, apparently mainly by 

 means of the minute podal hooks of the posterior segments of 

 the body. 



The mature worm (fig. 1) is from three to four millimetres in 

 length by about one-fourth of a millimetre in breadth, and is 

 divided into twelve segments, including the head. The color is 

 translucent olive-green, with the cephalic tentacles of a slightly 

 brownish hue. As the worm shortens, the segments become more 

 bulging laterally and the constricti6ns deeper ; in elongation, the 

 segments become more cylindrical and ' the constrictions less 

 marked. When the worm is elongated, it is of nearly uniform 

 width for about three-fourths of the length, and then slightl^'^ 

 tapers to the end, or is a little widened again in the two segments 

 before the last. The head is about as broad as it is long, and is 

 surmounted by a pair of lateral lophophores supporting the ten- 

 tacles. Its border above projects dorsally into a short rounded 

 process. The succeeding four segments of the body are about 

 as broad as they are long, and nearly of uniform size ; the next 

 one is somewhat longer than those in advance. The seventh 

 segment, in all the mature worms observed, greatly exceeded any 

 of the others. It was usually twice the length, and differed from 

 them in having an abrupt expansion at the fore-part, which sug- 

 gested the production of a head prior to division of the worm ; 

 a process, however, if it occurs in Manayunkia, I had not the 

 opportnnity of observing. The succeeding segments, smaller 

 than the anterior ones, differ little in size, except the last two. 

 The terminal segment abruptly tapers from above its middle in an 

 obtusely rounded extremit}^ When the worm protrudes from its 

 tube, the lophophores are reflected from the head, and they 

 exhibit a double row of tentacles extending forward. The num- 

 ber of tentacles varies with the age of the worm, but at maturit}?^ 

 there are usually eighteen for each lophophore. They are of 

 moderate length, and of uniform extent, and measure about half 

 a millimetre. Two of them internally, one for each lophophore, 



