KUTCHIN. — PERIPHERAL NERVOUS SYSTEM OF AMPHIOXUS. 601 



tissue. The nerves to the branchial basket pass upward along the 

 ligamentum denticulatum in numerous small threads, and enter the 

 basket not far from its dorsal region of attachment. The nerves in 

 the "pocket" portions of the ligament run more or less longitudinally 

 (Fig, 17), while those in the portions attached to the primary bars 

 take a nearly vertical direction. As may be noted in Figure 17, 

 nerves pass to the primary and secondary bars from various portions 

 of the ligament. Figures 14 (PI. 3) and 19 (PI. 4) show the nerve 

 threadlets of the primary and secondary branchial bars, and the 

 connecting threads passing along the cross-bars. These figures, 

 drawn from methylene-blue preparations, show an interesting likeness 

 to Dogiel's Figur 17rt, taken from a Golgi preparation. In the course 

 of treatment after impregnation with methylene blue, the branchial 

 epithelium sloughs off in large measure, exposing the nerve threads. 

 The nerves which pass dorsad along the primary and secondary bars 

 lie at first on the more exterior (lateral) surface of the branchial basket. 

 As the threads ascend, they gradually shift toward the interior, and 

 a greater number of threads are often found on the more posterior 

 portion of each primary bar. Near the top of the primary bar these 

 threads pass into a plexus lying between any given bar, and the next 

 posterior secondary bar (Fig. 20). It is quite possible that as many 

 fibers ascend on the anterior side of the bars to join this dorsal plexus, 

 but the specimens observed did not show as great a number. Nerves 

 passing along the secondary bars join this dorsal plexus with a smaller 

 number of threads. In the middle region of the branchial basket, 

 and in its ventral portion, the nerve threads lie on its more external 

 surface. The nerves of the primary bars are loosely placed, and form 

 an irregularly meshed network, the threads of which are not noticeably 

 arranged lengthwise of the bar (Figs. 17, 19). On the secondary bars 

 (PI. 3, Fig. 14), on the contrary, the slightly knotted nerve tlu'eads 

 form a plexus consisting of numerous long, longitudinally arranged 

 threads, connected by short branches. This plexus appears to be 

 rather smoothly drawn over the surface of the bar, in contrast to that 

 of the primary bars. The knotted appearance of threads on the 

 secondary bars may be an artificial condition. Nerve threads crossing 

 from one bar to another along the cross-bars form a plexus over the 

 latter in their course. At least, in the region dorsal to the ligamentum 

 denticulatum fibers pass from primary to secondary bars at other 

 points than the cross-bars, thus adding to the elaborateness of the 

 branchial plexus. 



I find a large number of the previously mentioned special nerve 



