KUTCHIN. — PERIPHERAL NERVOUS SYSTEM OF AMPHIOXUS. G07 



passed out into the swellings in the course of treatment with chemicals, 

 or upon pressure, and contrasted brilliantly with the light stain. An 

 excellent illusion was sometimes produced by the presence of well 

 stoned nuclei, wliich are either pushed out from the cord, or are 

 sheath nuclei. The weak osmic acid has little effect on tissues be- 

 neath the surface, and the subsequent washing in water causes actual 

 maceration. This would account for all manner of artifacts. The 

 specimens treated according to the gold-chloride method mentioned 

 above, show general distortion, and many structures are so displaced 

 as to make such preparations quite unreliable for study. These 

 bodies, if present in methylene-blue preparations, will persist when 

 the preparations are preserved in the mixture of glycerine and am- 

 monium picrate; but when fixed in ammonium molybdate and 

 dchydraied they usually disappear. Similar structures were never 

 found in well preserved and sectioned material. There seems, there- 

 fore, but little doubt that these so-called "ganglia" are artifacts. 

 Since writing the above account, Jolinston's ( : 05) paper was noted, 

 in which he also concludes that these structures are of artificial forma- 

 tion. Johnston finds a small proportion of the ganglion cells of 

 Amphioxus in the nerve cord, and the remainder in the dorsal roots, 

 located as far as, and beyond, the place of division into dorsal and 

 ventral rami. 



G. Structure of the Dorsal Nerves. 



In methylene-blue preparations of the dorsal nerves, darkly stained 

 fibers can often be traced from the neural tube, or place of exit of the 

 nerve, through the myoseptum to the "S'entral border of the lateral 

 muscle. These fibers are more or less separated from one another, 

 and are not of equal size. Usually a single fiber cannot be traced for 

 this entire distance. Fibers can frequently be discerned in the rami 

 cutanei ventrales which give these branches a darkly colored appear- 

 ance. I have often traced one, two or three fibers into the common 

 basal trunk of the descending and ascending visceral branches, but 

 was unable to trace distinct fibers into either of those branches. As 

 has been noted, however, these nerves sometimes present a fibrous 

 appearance. Figures 40 (PI. 7) and 22 (PI. 5) show fibers of at least 

 two sizes entering the dorsal nerve roots, the smaller fibers being by 

 far the most numerous. This agrees with the observations of Johnston 

 (:05). The different structural appearance of the \dsceral nerves 

 has already been noted. This difference is particularly evident in 



