732 



THE AMERICAN NATURALIST 



[Vol. XL 



Nervous Supply. — The protractors of the ribbon are supplied 

 by nerves from the cerebral ganglia. The cords supplying them 

 branch oflP from the two (one on either side) which go to the pro- 

 tractors of the cartilage. Where one of the latter passes under 

 the first cartilage protractor the cord comes off and, piercing a 

 few of the protractors near their origin, passes on to the surface of 

 the lingual protractors that lie upon the ramus, and then continues 

 on to the ventral sheet of cross fibers, which it supplies, and on to 

 the first pair of slender lingual protractors (Fig. 10, 7). As will 

 be seen on consulting the figure, a sort of parallelogram anasto- 

 mosis is formed by this nerve upon the ventral surface of the buccal 

 mass in its lower third. 



Musculature of the Proboscis, Nerve Supply 



The proboscis wall itself has a very well developed musculature. 

 This musculature is w^hite in contrast to the very red muscles of 

 the buccal mass. The innermost layer of the proboscis wall is 

 one of longitudinal fibers, next comes a tolerably thick circular 

 layer, and beneath the integument is found another longitudinal 

 layer. The contraction of the longitudinal layers serves, of course, 

 to shorten the proboscis and to increase its diaineter, wlicreas the 

 contraction of the circular layer would have the opposite ctlect. 



The innermost longitudinal layer (at least) is suppHcd by nerve 

 cords that spring from the cerebral ganglion and pass forward 

 along the esophagus piercing in their course the muscle cup at the 

 base of the proboscis. One of these cords passes along outside 

 the line of insertion of the cartilage protractors to the end of the 

 proboscis, giving off branches to the wall of the proboscis as it 

 proceeds (Figs. 5, 10, 4). Another cord passes along parallel to 

 the one just mentioned, but inside the line of insertion of the pro- 

 tractors of the cartilage (Figs. 5, 10, 3). Still another, which 

 sometimes, at least, comes off as a branch of the second, passes 

 forward a little farther in toward the mid-line and is covered, like 

 the second in its anterior portion, by muscle strands that pass 

 from the esophagus to the wall of the proboscis. 



At the base of the proboscis is situated the muscle cup already 

 mentioned, and which is composed of transverse fibers that mingle 



