No. 3] LOXOSOMA DAVENPORT!. 359 



ectodermal cells. These cells, usually three in number, have 

 deeply staining protoplasm and basal nuclei, and with their 

 distal ends surround a minute cavity with which the pore com- 

 municates. 



Musculature. — The most prominent part of the musculature 

 consists of fibers extending longitudinally just beneath the 

 epithelium (PI. XXXII, Fig. 15). They are attached about 

 the margin of the foot and extend upward to the lophophore, at 

 the margin of which those upon the anterior side become in- 

 serted. Those in the lateral and dorsal portions pass obliquely 

 outward into the marginal portion of the lophophore and help 

 to make up the atrial sphincter. At about the height of the 

 stomach the dorsal longitudinal fibers bend laterally to enter 

 the marginal portion of the lophophore, leaving the central 

 part of the organ immediately about the rectum free from 

 muscle fibers. It is obvious that the contraction of the longi- 

 tudinal muscle fibers causes a shortening of the body of the 

 animal, and in conjunction with the atrial sphincter, the closing 

 of the lophophore. 



Oblique muscle fibers are present in the lower portion of the 

 stalk, just beneath the longitudinal muscles, and chiefly upon 

 the anterior side. They are attached all around the margin of 

 the foot and extend obliquely upward and toward the anterior 

 side. Their obliquity is greatest near the foot, where those from 

 opposite sides cross in the median part of the ventral side. 

 Higher up the obliquity becomes less, and toward the stomach 

 the oblique fibers become nearly parallel with the longitudinal. 

 On the dorsal side of the stalk oblique fibers are present only 

 at the extreme basal portion where they attach at the margin 

 of the foot. These fibers may be assumed to be of service in 

 aiding the animal to turn and bend its body in various ways, 

 though I have seen no indication of their use in the manner 

 described by Prouho ('91) for corresponding muscles in L. anne- 

 lidicola. The latter species, which lives like L. Davenporti, 

 attached to a tubicolous annelid, can quickly rotate itself 180° 

 upon its base of attachment by the contraction of its oblique 

 muscles, and so assume the position in which it is least liable 

 to injury by the movement of the worm up or down in its tube. 



