KUTCHIN. — PERIPHERAL NERVOUS SYSTEM OF AMPHIOXUS. 573 



and these methods were found to give excellent results. Material was 

 also hardened in various fixing fluids, 10% formol proving to be 

 particularly valuable. The same methods were employed at Naples 

 upon Brancliiostoma lanceolatum, but a larger number of prepara- 

 tions was made, to provide against the uncertainty of impregnation. 

 Further discussion of these methods will be taken up in the body of 

 this paper, but a few general remarks are in place here. 



The best impregnations of both superficial and visceral nerves were 

 obtained by immersion of the li\ing animals in sea-water colored a 

 moderately dark blue with a stock mixture of ^% to 1% of methylene 

 blue in normal salt solution. The sea-water mixture should never be 

 opaque. It is probable that the small quantity of salt in the mixture 

 causes the epithelium to loosen, thus permitting more direct action of 

 the methylene blue. Such preparations are not, of course, suitable 

 for study of sensory endings in the skin. Specimens immersed in this 

 mixture do not appear impaired in vigor at the end of two or three 

 hours. The subsequent exposure to air recommended by Dogiel 

 ( : 02) is of great importance ; the length of time required for different 

 nerves can be determined only by continued observation under the 

 microscope. The specimen must be kept moist with the methylene- 

 blue mixture during such exposure. Fixation was usually effected by 

 the ammonium-picrate method, and it was found that the addition of 

 a few drops of 1% osmic acid to each 100 cc. of the ammonium picrate 

 used for fixing these preparations greatly aided in their preservation. 

 Material treated in this way, preserved in the usual ammonium- 

 picrate and glycerine mixture, and carefully guarded against unneces- 

 sary exposure to light, was found in excellent condition at the end of 

 two years, while other preparations fixed without osmic acid were 

 practically useless after one year. 



The gold-chloride method recommended by Hardesty ( : 02) for use 

 after fixation with 10% formol proved useful in demonstrating motor 

 fibers and their endings. I regard this method as worthy of wider 

 use because of its accurate fixation and the comparative absence of 

 artifacts. The action of the gold chloride is, however, no more certain 

 in this method than in others. 



Mallory's ( : 00) method for study of the central nervous system 

 proved useful in the case of Amphioxus for the peripheral nervous 

 system. Vom Rath's fluid (strong) was employed, but with indiffer- 

 ent results, except for the central nervous system. The methods of 

 Golgi for impregnation with silver, and their various modifications, 

 are all useful in obtaining impregnations of different parts of the nerv- 



