SECT. IV 



THE MUSCULATURE 



61 



surfaces of attachment. They are, in fact, so far at 

 least as they are composed of longitudinal muscles, 

 nothing but the elements of the dermo-muscular tube 

 drawn out of their position, as may be clearly seen 

 from Fig. 12, which gives a general view of the whole 

 musculature. The same fact might also be concluded 

 from their great number, disorder, and want of con- 

 centration. When, however, we have to decide which 

 muscles belong to the circular and which to the 

 longitudinal layer, the following seems to be the 



FIG. 16. Diagram to explain the courses of the muscle bands in B and C, Fig. 15. 

 i represents an Annelidan parapodium in its original horizontal position with 

 three longitudinal muscle bands running into it. 2 represents the same drawn 

 down to form a limb of Apus. 



principle of arrangement. The muscles which enter 

 the dorsal side of the limb with broad insertions on 

 the soft integument of the dorsal surface (Fig. 15, A) 

 are probably elements of the circular muscle layer ; 

 their position close under the lateral integument 

 favours this derivation (Fig. 14, cm. ; cf. also Fig. ii). 

 On the other hand, we find on each side of the limb 

 a number of muscle bands with more definite points 

 of insertion ; these are attached dorsally to the sides 



