INTRODUCTION. 



At Professor Brooks 1 suggestion I undertook a study of the eye of 

 salpa in connection with his more extensive study of the genus. In the 

 course of the work I discovered that salpa shows a more or less well- 

 developed sub-neural gland, a point of so much interest that I include a 

 description of this organ in the present paper. I am indebted to Prof. 

 Brooks for the material upon which I worked and for the use of his own 

 prepared sections of the embryos and developing stolons of Salpa pinnata. 

 During the progress of this work I have received much assistance from 

 him as my instructor, and I take this opportunity to express to him my 

 warmest thanks. 



The extensive collections of salpa made by the United States Fish 

 Commission, which were placed at the disposal of Professor Brooks and 

 upon which the investigations here recorded were made, include the 

 following species i 1 



Cyclosalpa 2 pinnata, Forsk., solitary and chain forms. 



Cyclosalpa Chamissonis, Brooks, chain form. 



Salpa cylindrica, Cuv., solitary and chain forms. 



Salpa runcinata-fusiformis, Cham., solitary and chain forms. 



Salpa africana-maxima, Forsk., solitary and chain forms. 



Salpa costata-Tillenii, Quoy and Gaim., solitary and chain forms. 



Salpa hexagona, Quoy and Gaim., solitary and chain forms. 



Salpa democratica-mucronata, Forsk., solitary and chain forms. 



Salpa cordiformis-zonaria, Quoy and Gaim., solitary and chain forms. 



Salpa scutigera-confederata, Cuv., solitary and chain forms. 



Salpa bicaudata (?), Quoy and Gaim., chain form (probably to be 

 regarded as a very distinct variety of Salpa scutigera-confederata). 



METHODS. Tunicate tissue is so easily manipulated that the simplest 

 methods have given the best results. For staining, Kleinenberg's 



1 1 have followed for the most part the nomenclature given by M. P. A. Traustedt 

 [19]. (See list of papers referred to at the end of this memoir.) 



* Whether the group cyclosalpa be regarded as a separate genus or as a sub- 

 division of the genus salpa, it is convenient for the purposes of description in this 

 paper to distinguish between the cyclosalpas and the salpas. 



