VI 



NEMATODA MUSCLES 



129 



The contractile portion consists of a number of columns, very 

 regularly arranged in two rows and close together, but allowing 

 sufficient space between adjacent 

 columns for fibrils of the spongio- 

 plasm to penetrate ; and these be- 

 come continuous with the fibrils 

 of the sub-cuticle, which is thus 

 intimately connected with both 

 nervous and muscular systems. 



The medullary portion of the 

 cell varies greatly in size ; it may 

 stretch far into the body-cavity, 

 which may be thereby almost oc- 

 cluded, or it may be flattened out, 

 leaving a large space around the 

 alimentary canal. .At one point, 

 usually about its middle, it is 

 produced into a process, which 

 bends inwards towards the dorsal 

 or A^entral nerve - cord, and by 

 means of this process the muscle 

 receives its nerve supply. 



In most Nematodes there are 

 numerous muscle-cells to be seen 

 in any transverse section, forming FlG ^ 

 a layer within the sub - cuticle, 

 and broken up into four quad- 

 rants (Fig. 62) by the projec- 

 tion of the dorsal, ventral, and 

 lateral thickenings of the sub- 

 cuticular tissue. In some genera, 

 however, such as Oxyuris, Strongylus, Pelodera, Leptodera, etc., 

 there are but eight muscle-cells in a row, two in each quadrant. 

 Such genera are classed together by Schneider, 1 and termed 

 Meromyarii (vide p. 137). 



In addition to the characteristic muscles of the body-wall 

 there are others, such as those which move the spicules in the 

 male, which cross the body-cavity obliquely near the anus, and 

 such as sphincter muscles near the latter orifice, which have not 



1 Monographic der Nematoden, 4to, Berlin, 1866. 

 VOL. II K 



A, transverse section through 

 the centre of a muscle-cell ; B, the 

 same through a nerve fibre showing 

 the sub-cuticular fibres running into 

 the sheath. * (After Rohde.) a, 

 Cuticle; b, sub-cuticular fibres continu- 

 ous with d ; c, contractile columns ; 

 d, network of spongioplasm ; e, 

 nucleus. 



