No. 2.] ANA TOM V OF BDELLODRILUS ILLUMINATUS. 505 



give rise to long slender ductules, which, first united into fasci- 

 cles, break up into smaller and smaller groups, and are finally 

 distributed singly on all parts of the surface of the acetabulum. 

 This arrangement is beautifully shown in living specimens. 

 The ductules are filled with rounded granules, which may be 

 forced from their mouths in living worms by pressure. The 

 granules will emerge in strings, absorb water, swell, and run 

 together in a very short time, forming a homogeneous mucus. 



Of all the numerous glands developed from the epidermis 

 none are so remarkable as the great lateral mucous glands, 

 whose clearness in living examples suggested the specific name 

 for the species. Each of the post-cephalic somites, from the 

 first to the ninth, inclusive, possesses a pair of these structures, 

 which occupy, in the more anterior ones, almost the entire 

 body-cavity of the major annuli, lateral to the heart, alimentary 

 canal, and nerve cord (Fig. 7, Ig). Of more or less spherical 

 or broadly fusiform shape, they pass dorsally and ventrally into 

 fascicles of ductules which perforate the body walls, and open 

 on the surface between two circular muscle fibres (Figs, i and 

 7, Ig). Occasionally, instead of a single gland, there are two 

 pyriform ones, placed end to end and more or less united (Fig. 

 I, lg8), or the cells may have this grouping within a single 

 gland. The external openings are seen in surface views as 

 four series (two dorsal and two ventral) of clear sieve-like spots, 

 in which the ends of the ductules appear as 10-15 clear polyg- 

 onal areas in a stained meshwork (Figs. 6 and 7). The ductules 

 have a terminal diameter of .002 mm. 



The exceedingly large gland cells, which often have a diam- 

 eter much exceeding that of the entire nerve-cord and ganglia, 

 that is, about .05 mm., have an irregularly polyhedral shape; 

 their broad bases being fitted together to form the surface of 

 the gland, near which the nuclei lie; while internally they 

 taper into the ductules which frequently traverse the entire 

 length of the gland, and emerge with the fascicle at the oppo- 

 site pole, often having a complete length of .1 mm. The cell 

 protoplasm is faintly granular, and very transparent; and is 

 very slightly, or not at all, affected by stains. Of all the stains 

 which were used methyl green alone gave a decided color. 



