444 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 22, NO. 12 



vglmal 



/JffltSt'" 



cement-like secretion of the three caudal glands to pour outward to be used in 

 temporarily cementing the nema by the tail to the substratum in a versatile 

 manner. The spinneret and associated glands are of vital importance to 

 aquatic nemas; and this apparatus is all but universal among them. The 

 three elongated ellipsoidal caudal glands, 84, 88, 90, the remotest of them 

 ten body-diameters in front of the anus, are scattered in a loose tandem in 

 the ventral part of the body cavity. Their ducts, 18, 86, leading to the spin- 

 neret, can be distinctly seen under some circumstances. Most of the caudal 

 setae on the female are reduced and inconspicuous. 



It is the sticky nature of the secretion of the caudal glands that enables 

 these nemas to ensconce themselves so securely in the midst of the elements of 

 the mud in which they live. By its aid they attach themselves to the sub- 

 stratum, especially in times of danger, and to each other. By means of this 

 cement, they bind themselves together with mud etc. in almost inextricable 

 tangles. 



The two very thin ribbon- 

 like lateral cords, 3, 93, of 

 Metoncholaimus pristiurus, 

 one on each side, imme- 

 diately under the cuticle, 

 are about half as wide as 

 the body, each cord consist- 

 ing of three regions, a me- 

 dian region composed of a 

 single broad row of quadrate 

 cells, and a row, less than 

 half as wide, on each side of 

 it. In the anterior part of 

 the body the quadrate cells 

 are usually a little longer 

 than they are broad, in the 

 posterior part a little shorter 

 than broad. As stated, 

 these median cells are 

 flanked by two much nar- 

 rower longitudinal series of 

 cells, having the same gen- 

 eral composition, i.e. a very 

 fine protoplasmic network 

 (meshes two microns to 

 five microns) in the inter- 

 sections of which are roundish or somewhat ellipsoidal yellowish granules, 

 usually not equidiametral. Even without staining, there are also to be 

 seen, at least in each of the cells composing the central row of the lateral 

 cord, faint indications of a nucleus; these indications in the living nema con- 

 sist in an almost entire absence of the reticulation which is to be found else- 

 where in the cell. These cells of the lateral cord are necessarily very flat; 

 that is to say, their depth (radially to the nema) is much less than their diam- 

 eter in either of the other two directions, i.e. longitudinally to the nema or 

 tangentially. The division line between the central row of cells and the 

 narrower ones on the margin is an almost invisible, very thin, somewhat 

 indirect cell-wall line. Around the outer margins of the two outer rows of 

 cells the granules are slightly differentiated from the other granules; so that in 



IB mem 

 n jar Am 



& rectum 



u 



Fig. 2 Tail of fe- 

 male M. pristiurus, X 

 325; showing the mi- 

 nute but important 

 spinneret valve, vlv 

 spn, and the muscular 

 strand leading from it 

 into the midst of the 

 3 ampullae of the 

 caudal glands; shown 

 light in the midst of 

 the spinneret. Note 

 the pylorus at pylor. 



.spnn 



spn 75 



