SECT. IV 



THE MUSCULATURE 



55 



muscles which arc still functional, i.e. those which 

 diverge in the transverse plane. 



Let us now compare this sketch with the muscula- 

 ture of the Apoclidai (Figs. 12 and 13). The dorsal 

 longitudinal bands in the head region, after springing 

 across the opening into the interior of the shell fold 

 of the fifth segment, arc attached to the forehead by 

 numberless fine fibres of connective tissue, so that it 



/;- y-/-.. \ \ wHj^iJiriss^fifiKBWSssssiS- - 





SSteS 



vm v 



FIG. 12. Section through a specimen of Apus cancriformis, partly diagrammatic, to 

 show the longitudinal musculature. Anteriorly the dorsal bands are stretched 

 round the bend of the head, the ventral bands of the five segments being clumped 

 into a sinewy mass, the sternal plate. Posteriorly the two unite round the body 

 to form a dermo-muscular tube, drn, dorsal ; z//, ventral muscle bands ; s, shell ; 

 r, eye ; /, under lip ; ;;/], ;//o, ist and and maxilla; ; ?>, ventral parapodia of trunk 

 limbs ; 6 ditto of ist trunk limb. The live original anterior segments of the 

 Annelid indicated by dotted lines. 



is not at first apparent that the two strong bands 

 which start a little in front of them from very 

 scattered points of insertion on each side of the eyes, 

 running clown over the oesophagus to be attached in 

 front of the prostomium, are really a continuation of 

 the dorsal bands. That this is the case, however, is 

 clear from Fig. 13. We see here not only the dorsal 

 bands themselves lengthened to pass round the curve 



