254 E. S. GOODRICH. 



corpuscles^ renders it very difficult to make out the details Of 

 its anatomy in the living animal. 



The prostomium (figs. 2 and 6, pr.) is rather large and 

 conical. Each segment, from the second, is provided with two 

 dorsal and two ventral bundles of setae (fig. 2, I. d. s. and 

 I. V. s.), placed in a transverse section nearly at the four corners 

 of a square. Each bundle contains from two to five setae, 

 generally three. All the setae, both dorsal and ventral, are 

 alike S-shaped in outline, with a thickening about one third of 

 the way from the distal end, which is bifurcate (fig. 3) ; they 

 are of the ordinary Tubificid furcate type. 



On close examination in a favourable light it is seen that the 

 whole worm is clothed from head to tail in a more or less 

 dense furry covering of hair-like processes, closely set, 

 extremely fine, and apparently of cuticular origin (fig. 4, pel.). 

 These hair-like structures are not cilia ; they do not move, and 

 are not protoplasmic. Resembling the so-called " sense-hairs ^' 

 or palpocils found on the prostomium and first segments of 

 most aquatic Oligochaetes, they are probably homologous with 

 these, but developed to an extraordinary degree. The cuticle 

 itself (fig. 4, c.) presents no peculiarity. The epidermis (figs. 

 4 and 7, ep.) is formed of regular more or less cubical cells, 

 with large oval or round nuclei. Below the epidermis is a 

 narrow layer of circular muscles (fig. 7, c. m.) within which 

 are the longitudinal muscles (fig. 7, /. m.). In the transverse 

 section the contractile fibrils are of different heights, being cut 

 through at various distances from the middle of the cells which 

 bear them. Along each side, about halfway between the 

 dorsal and ventral bundles of setae, the layer of longitudinal 

 muscles is interrupted by a row of cells forming the lateral 

 line (fig. 7, /. /.). Dr. Hesse has recently shown (4) that these 

 are the cells to which belong the circular muscular fibres ; my 

 preparations support this view. Lining the inside of the body- 

 wall is the ccelomic epithelium, composed for the most part of 

 large vesicular cells (fig. 7, c. ep.). 



The coelomic corpuscles, which as above stated are very 

 numerous, are spherical and coarsely granular (fig. 28, c. c). 



