BUENE : ANATOMY OF IIANLEYA ABYSSOllUM. 



11 



in different species of Chiton. Brandt,^ in Cliiton fascicularis, and 

 later, Von Jhering,- in Chiton squamostts, described two commissures 

 uniting the buccal ganglia to one another — a posterior passing, as 

 usual, between the oesophagus and the radula sheath ; and an 

 anterior connecting the buccal ganglia across the anterior region 

 of the roof of the buccal chamber. Bela Hallcr,^ on the contrary, 

 says that in Chiton fascicularis and C. siculus there is no anterior 

 commissure, and that it was probably an erroneous observation of the 

 oesophageal nerves that led Brandt and Von Jheriug to the description 

 of a non-existent structure. 



From my dissections of this region in Hanlcya ahyssoriim, thci-e 

 seems to be no doubt that the latter observers were not mistaken ; 

 in this species the anterior commissure is not only easily traced 

 from ganglion to ganglion, but the whole thing can, with a little 

 care, be removed entire* (Fig. H, a.h.c). 1 have also seen this 



Fig. II. — Auterior pni'tiou of uervoiis system of Ifffy^/^/rt ff%s.9or«;«. x 4. From 

 Nos. laOo C aud D. E.C.S. a.h.c. auterior buccal commissm'e. 

 h.r/. buccal ganglion. l.n. lateral nerve-cords. «;'.«. cesopliageal 

 nerve. j;.c. anterior pedal commissure, -p.c'. roots of one of the 

 succeeding pedal commissures, p.n. pedal nerve-cord. 



commissure, though with greater difficulty, in Criiptoplax striatus. 

 In a point of this kind it is not at all necessary that one or other of 



' E. Brandt, " Ueber dus Nerveusystem von Cliiton fasclcuhiris " : Bidl. Acad. 

 St. Petersb., xiii, 18G9. 



^ II. V. Jhering, " Beitriige zur Kenutuis des Nervcnsystems der Amphiueiu'en," 

 etc. : Morph. Jalirb., iii, 1877, p. lo7. 



3 Haller, " Der Chitoneu der Adria." Ft. 1: Arb. Inst. "Wien, iv, 1882, p. 7. 



■* No. 130oD, Physiological Series, Roy. Coll. Surg. Museum. 



