72 



BRISTOL. 



DESCRIPTION OF PLATE VIII. 



Fig. i8. A projection of the nerves of the fifth and following first annul! 

 showing especially the intermuscular nerve ring and its relations to the central 

 nervous system. On the ring are ten (five in the half section) groups of bipolar 

 cells designated as below. The trunks from the central system join the ring at 

 the points marked i to 4 on the margin, which points also mark the points of junc- 

 tions of the long bipolar cells with the ring. The numerals in the figure designate 

 the bundles of longitudinal muscles, here seen in section, and drawn only in three 

 of the ventral bundles. In these are shown fibrillae which leave the ring to 

 innervate the muscle cells. The layers of circular and oblique muscles between 

 the epidermis and the long muscles are omitted for clearness, in order to show 

 the fibers from the sensillae to the ring. 



ABBREVIATIONS. 



al. 



br. to 1st ann. et seq. 



epi. 



gn- 



l.v. 



med.bdl.l.m. 



m.circ. and ob. 



sens. /, //, ///. 



in.v.b.p.c. 



o.v.b.p.c. 



in.d.b.p.c. 



o.d.b.p.c. 



lat.d.b.p.c. 



1-4, marginal. 



1-6, within. 



intestine. 



branches of nerves to the respective annuli. 

 epidermis, 

 ganglion. 



lateral blood vessel. 

 median bundle of long muscles, 

 layer of circular and oblique muscles, 

 three types of sensillae. 

 inner ventral group of bipolar cells, 

 outer " " " " 



inner dorsal " " " 



outer " " " " 



lateral " " " " 



junctions of ring with central system and the long con- 

 nective bipolar cells. See PI. 11, Junctions, 

 ends of the bundles of long muscles. 



Outlines taken from camera drawings. 



Fig. 19. Camera drawings of a section showing details of the sympathetic 

 system. The faint circles are the cut ends of muscle cells. In many of them 

 may be seen the nerve end plates. The wide bundle of fibers is part of the lateral 

 bundle. See PI. VII, Fig. 17. Reichert, yV immersion, oc. 3. 



Fig. 20. Dorsal view of part of the collar and sympathetic system. From a 

 flattened head killed in Perenyi's fluid and viewed as a transparent object in 

 Haller's fluid. It shows the continuity of the dorsal branches of the sympathetic, 

 the ganglionic masses under the collar (Pl.VII,Fig. 17), and the different character 

 of the fibrous bundles running to the buccal cavity and the plexuses posterior to 

 the collar. Zeiss, c. oc. 2, camera drawing, reduced nearly one-half. 



