No. 3. — On Nectonema agile, Verrill. By Henry B. Wakv.' 
CoNnTENTS 
Page Page 
J-introduction - 2.2. . );.1¢0 4. Body Cavity .. . . 188 
Methodee re Lis 2 188 5. Nervous System .. . 159 
Al Systematie 12> 82/82 1ST ay DY ainene . 159 
III. Biology. . . Sy. Si) 139 a Ganglion Cells . 159 
IV. General Morsholiay egy tet el aO B Dorsal Cells . 165 
1 bexteriale > o.oo ae ae y. Fibrous Mass . 166 
2. Internal . . 3, aes, esl eo b. Ventral Nerve Cord 167 
V. Anatomy and Hieidlogy™. Peas c. Anal Ganglion . . 169 
PeBody Wall’. +s) S0. eas 6. Sexual Organs. . . . 171 
9. utiewla, of! 3 iy i4d aMale 415 20%. oso 
a. Bristles.. . - 144 be Female. 0 4: = <.pia 
B Seales. . 1461 ° Wi Discussion =." fs = i eke 
b. Hypodermis . . . 146 t. Dorsal Cella. oo a 
a Median Lines . 146 2. Large Ganglion Cells . 180 
c. Muscular Layer . . 148 3. Rows of Hairs. . . . 181 
2. Alimentary Canal . . 151 4 Muscular Layer . . .« 181 
a. (Esophagus . . . 151 5. Parasitic Nature . . . 182 
b. Intestine . . . . 154] VII. Comparison with other Forms 182 
3. Anterior Chamber . . 156| VIII Bibliography . . . . - . 188 
Explanation Gf Pig ures: oo i. 1s) el he tees Matas ay = ites i's) pte noses 189 
I. Introduction. 
For more than twenty years an interesting pelagic worm has been 
frequently captured at the Newport Marine Laboratory. It was proba- 
bly first seen by Dr. Alexander Agassiz, who encountered it as early as 
1870. His first recorded observations, made in 1871, as well as his 
subsequent studies, have remained, however, in the form of unpublished 
notes and drawings, which were placed at my disposal in June, 1891, 
when I began the present study. Two of these drawings, which illus- 
trate most clearly the external appearance, and show also some of the 
internal organs, are reproduced on Plate I. Figs. 3, 6. 
In 1873 Professor A. E. Verrill published, under the title “‘ gen. indet.,’ 
a short description of two specimens captured in towing near Wood’s 
1 Contributions from the Zovlogical Laboratory of the Museum of Comparative 
Zovlogy, under the direction of E. L. Mark, No. XXXII. 
VOL. XXII]. — NO 3. 10 
