730 



THE AMERICAN NATURALIST 



[Vol. XL 



criss-cross strands. Also, the two sheets of cross fibers, dorsal 

 and ventral, serve on contraction to give stiffness to the cartilage 

 frame as a whole and to prevent its buckling. 



Nervous Supply of the (heat Retractor. — The great retractor 

 muscle is supplied from the stout nerves that leave the buccal 

 ganglia and run forward to penetrate the lateral halves of the 

 median root, and then to continue on to the other roots, and also 

 to the retractors of the cartilage (Fig. 10, 5). 



Protractors. — The protractors of the lingual ribbon are six quite 

 distinct long slender muscles that are found on the ventral side 

 of the buccal mass and of the odontophoral cartilage. There are 

 three on either side of the mid-line (Figs. 10, 11, prr., a, h, c). 



,TrT.(h) ,r^.(c) 



The protractors arise from the m('nil)riiii()i 

 anterior part of the ribbon is found, and t 

 straight backwanl. 



(1) The most ventral muscles are a pair 

 red bands along the mid-ventral line of the 

 by a white line (blood vessel) (Figs. 10, 11, 

 from the ventral surface of tlie menibrai 

 backward, adherent to the ventral slieet of 

 with the lateral halves of th(> median root o 

 the ra.lula. 



passes back along tlu 



