572 PROCEEDINGS OF THE AMERICAN ACADEMY. 



I wish to express my sincere thanks to that institution for the excep- 

 tional opportunities afforded by the fellowship. Professor E. L. 

 Mark of Harvard University suggested this field for investigation, and 

 I am also indebted to him for kindly advice and criticism. The work 

 was carried on in 1904-1905 at the Bermuda Biological Station and in 

 the Harvard Zoological Laboratories while I was registered as a 

 Graduate Student in Radcliffe College. In the spring of 1905 the 

 problem was continued at the Naples Zoological Station, through the 

 kindness of the " Association for Maintaining the American Women's 

 Table at the Zoological Station at Naples and for Promoting Scientific 

 Research by Women." I am under obligation to those in charge of 

 the Naples Station for many courtesies extended throughout my stay. 

 During the year 1905-1906 laboratory privileges were kindly afforded 

 me for further work in the Zoological Laboratories of the University 

 of Chicago. 



Two species have been used as a basis for study, the Caribbean 

 Amphioxus, Branchiostoma caribaeum, found in Bermuda waters, and 

 the form so abundant at Naples, Branchiostoma lanceolatum. 



Literature. 



Retzius ('91) and Dogiel (: 02) have reviewed the literature on the 

 peripheral nervous system of Amphioxus in considerable detail, pre- 

 senting particularly points where lack of agrreement exists. Other 

 authors, as Rohde ('88) and Heymans et van der Stricht ('98), give 

 historical accounts in connection with their personal observations. 

 It is therefore unnecessary to give here a connected discussion of the 

 literature; the work of the several authors will be taken up in connec- 

 tion with each question in its bearing upon the descriptive part of this 

 paper. An extensive bibliography of Leptocardii is given by Lonn- 

 berg (:01— ,pp. 206-214). 



Material and Methods. 



At the Bermuda Biological Station the tissues of a large number of 

 Branchiostoma caribaeum were impregnated with methylene blue by 

 the mtra-vitam method. Gold chloride and the methods of Golgi were 

 also extensively used. Many variations were employed in the use of 

 all these methods, with the view of bringing out details of structure. 



