606 PROCEEDINGS OF THE AMERICAN ACADEMY. 



F. Spinal GancjUa. 



Dogiel ( : 02) found special structures in connection with the dorsal 

 nerves of Amphioxus which he interprets as spinal ganglia. Thuse 

 bodies appeared in specimens immersed from 3-6 hours in a dark l)lue 

 or violet mixture either of a 1% methylene blue, or of a saturated 

 solution of toluidin blue, in normal salt solution. They could also be 

 seen in gold-chloride preparations when the lemon-juice and formic- 

 acid method was used. These so-called ganglia consist of groups of 

 from 3 to 7 round, oval or pear-shaped elements, situated at the place of 

 exit of each dorsal nerve from the myoseptum, or near the proximal 

 end of the dorsal or ventral ramus where it gives off small branches; 

 in addition to these, similar, though smaller, bodies may be found even 

 as distant as the ventral border of the trunk muscles. These struc- 

 tures are illustrated in Dogiel's Figures 20, 21, 22a, 226, 22c, 22d, and 

 23. 



By using Dogiel's methods I was able to observe these structures in 

 methylene-blue and in gold-chloride preparations, and also found them 

 in specimens fixed in weak osmic acid and stained with picro-carmine. 

 They appeared not only at the places indicated by Dogiel, but by 

 using strong light for study of the preparations, they w^re found at 

 almost any point in the course of the dorsal nerves. In methylene- 

 blue preparations the size and number increased with the length of 

 immersion. These bodies were of varying size, in some cases quite 

 large, while by using the higher magnifications on portions of tissue 

 mounted under a cover-glass, similar structures of minute size could 

 be seen in connection with the smaller nerve branches. Strong light 

 revealed great numbers of these structures in connection with the nerves 

 of the thicker parts of the body. The methods mentioned abo^■e 

 always cause a marked enlargement of the ampulla-like dilation at the 

 posterior end of the neural tube, and a general increase of size in the 

 tube itself. These facts led to doubts as to the reliability of such 

 methods, and numerous experiments were made in the spring of 1905 

 to determine the nature of these bodies. Dogiel's methylene-blue 

 method, employing normal salt solution instead of sea-water, causes 

 general swelling of the tissues, and in some cases death occurs, followed 

 by certain post-mortem changes, before these bodies appear. In 

 material "fLxed" in weak osmic acid and stained with picro-carmine 

 these structures were frequently present, or, if not, I was able at will 

 to make them appear by pressing lightly on the cover-glass over the 

 mounted specimen. In some cases the pigment of the neural tube had 



