Pomona College, Claremont, California 83 



down the lateral and ventral walls of the oesophagus and originat- 

 ing in the lateral nerves of the visceral ganglion. 



(b) The maxillary and superpharyngeal system originate in 

 the main \isceral ganglion which is situated just below the brain. 

 The maxillary system branches repeatedly and serves the complex 

 maxillary musculature. The superpharyngeal system goes straight 

 back to where the intestine folds off. Here it developes a pair of 

 slender ganglia which form a nearly complete circuminestinal ring 

 and send off branches to the wall of the intestine. 



4. The muscle which causes extrusion of the teeth is attached to 

 the mandibular plates. It is a spindle-shaped muscle but acts by an 

 increase of length instead of a contraction as is usual in muscles of 

 this shape. This expansion is possible through the fact that the 

 muscle fibers run across the muscle instead of from origin to inser- 

 tion, and from the fact that the whole muscle is enclosed in a thick 

 envelope of tough connective tissue, which holds the muscle rigid 

 when a contraction of the fibers lessen the diameter and increase 

 the length of the muscle. This adaptation seems to render pre- 

 hension more efficient. 



BIBLIOGRAPHY 



Ehlers, E. 1864-69 



Die Borstenwurmer (Annelida Chstopoda) nach S\'stematischen 

 und Anatonschen Untersuchen Dargestellt, Leipzig, Engelmann, 

 748 pp. 24 Taf. 



Ehlers, E. 1892 



Die Gehoroggane der Arenicolon. Zeit. Fiir Wiss. Zool. Band 

 53, pp. 217-285, Taf, XI-XIV. 



Faivre, Ernest 1856 



Etudes Sur. THistologie comparee du systeme nerveux chez quel- 

 ques Annelides. These presentee a la faculte des sciences de Paris. 



Haller,B. 1889 



Beitrage zur Kentniss der Textur des Central Nervensystcms 

 Hoherer Wiirmer. Arbeit Zool. Inst. Wein. Tome 8, Heft 2, 

 pp. 175-312 Taf. 16-20. 



Lewis, M. 1898 



Studies on the central and peripheral nervous systems of two poly- 

 chaete annelids. Proc. Amer. Acad. Arts Sci., vol. 33, No. 14. 

 Apr., 1898, pp. 226-267, pi. 1-8. 



