142 BRODE. [VoL. XIV. 
I. INTRODUCTION. 
Tuis paper embodies, in part, the result of three years’ work 
carried on in the Zodlogical Laboratory of the University of 
Chicago and at the Marine Biological Laboratory at Wood’s 
Holl, Mass. 
During the entire time the work has been conducted under 
the supervision of Dr. C. O. Whitman, Head Professor of 
Zodlogy at Chicago and Director of the Marine Biological 
Laboratory, at whose suggestion the work was undertaken. It 
has been a great source of pleasure to me to be under the 
direction of so able a teacher, and I am very deeply indebted 
to him for the interest he has taken in my work. 
I desire also to express my gratitude to the authorities of 
the University of Chicago for the favors which they have from 
time to time granted me. 
My early studies on this annelid were with reference to the 
process of multiplication by fission. In the course of this study 
it became evident that a very exact knowledge of the anatomy 
of one segment was necessary in order to understand fully the 
changes which take place when a fission zone forms in a seg- 
ment. This study led to the working out of thenervous system 
entire and the distribution of the sense organs, together with 
some points on the general morphology of the worm. 
I have made many observations on worms undergoing fission 
and hope at some future time to bring out a paper on normal 
and artificial fission and regeneration. 
II. GENERAL REMARKS. 
I. CLASSIFICATION. 
Dero vaga was originally described by Joseph Leidy in 18801 
under the name Azlophorus vagus. The generic name Aulo- 
phorus was given by Schmarda? in 1861 to a form differing 
1 Jos. Leidy, Notice of Some Aquatic Worms of the Family Naids, dmer. Vat., 
Vol. XIV, No. 6, 1880. 
2 C. Schmarda, Neue wirbellose Thiere, beobachtet und gesammelt auf einer 
Reise um die Erde (1853-57), Theil I, Heft I, Leipzig, 1861. 
