416 THE AMBULATORY TUBES 



sublateral groups of glandular cells and four subdorsal groups, cor- 

 responding to a similar grouping of the six pairs of adhesion tubes. 

 The glands of the cephalic sole are sometimes rather more strongly 

 stained than those of the posterior sole in the same specimen, but 

 present the same general anatomical and histological structure. 

 Referring to the dorsally sublateral cervical glands as examples (see 

 Fig. 1), these are distinctly granular in structure and apparently 

 duplex, that is, have a well marked constriction near the middle, on 

 opposite sides of which, fore and aft, is a considerable volume of 

 nuclear (?) matter; the remaining portion of the cells is rather coarsely 

 granular, the granules measuring nearly l/j. in diameter. This duplex 

 glandular mass is hah" as long as the neck and anteriorly tapers to a 

 tubular portion not much wider than one of the cervical annules. 

 This narrow portion of the gland in turn tapers to a very narrow duct 

 about 2ju in diameter, which swells to form a fusiform duplex ampulla 

 as wide as one of the coarser cervical annules. The ampulla empties 

 forward through a short narrow duct, 1 to 2 /j. wide, directly into the 

 base of the corresponding adhesion tube, where a little stained matter 

 may usually be seen. The adhesion tubes reach exactly to the lips, 

 so that their outpour is practically terminal. All these details are 

 shown on a small scale in Fig. 1, ampullae reduced to two dots. 



The distal extremity of the ambulatory tube is somewhat bell- 

 shaped, and the lumen of the tube is prolonged into the cavity of the 

 bell through a short conoid extension. The significance of this bell- 

 shaped structure remains more or less problematical. No elements 

 have been seen in the tube, or hi the bell, that could be regarded as 

 contractile, and one therefore seems obliged to assume that whatever 

 changes of form are exhibited by this bell-shaped structure are due to 

 such factors as its own elasticity, the pressure of the internal secretion 

 and counter pressure of the external water. It would seem advan- 

 tageous to the nema if the secretion which flows out through the bell- 

 shaped organ could be "cut off" at will, and it is conceivable that this 

 bell-shaped affair in some way accomplishes that end. Again, it is 

 conceivable that the bell may mechanically give to the end of the tube 

 a greater adhesiveness, conceivably through suction, a suction that 

 might be made to vary with the relationship of the distal end of the 

 tube to the substratum, as in the familiar elastic concave rubber 

 suction disc. 



The facts that the setae of the inner rows are always the shorter, 

 and that all the setae are incurved, suggest that a suitable substratum 

 may be a microscopic filament, or a thin edge of something. This 



