NOE 2] THE MORPHOLOGY OF DERO VAGA. 161 
differ in histological structure. The only difference lies in the 
fact of the different external appearance of the organs. How- 
ever, since it is probable that all the Oligochaetes possess 
“touch organs,” the fact of their presence alone cannot be 
used as a character in determining relationships in genera 
and species. 
(c) Metameric Sense Organs. 
Oligochaetes. — Segmentally arranged sense organs have been 
described in Wazs appendiculata and Nats lurida. In the former 
they are said to be arranged in a band passing through the setae. 
There are from fifteen to twenty organs in a band. In the 
latter they are said to be in two bands made up of six to eight 
organs each. The arrangement of organs in WV. appendiculata, 
as figured by Vejdovsky,’ is very similar to that in Dero vaga 
in the band passing through the setae. 
Miss Randolph? has described metameric organs in two 
species of Tubificidae where they are arranged in two bands, 
one through the setae and one near the dissepiment. In one 
species there is a showing of a third band. She does not 
mention the number of organs in a band nor give their arrange- 
ment. 
Vejdovsky * mentions a single pair of organs in every seg- 
ment in Lumbriculus, Claparedilla, and Rhynchelmis in the 
lateral-line region. In Benhamia, Eisen* figures a band of 
sense organs about the middle of every segment. 
Miss Langdon ® and Hesse® both describe three bands of 
sense organs to a segment in Lumbricus. Hesse finds the 
number of sense organs to be the same on the two lateral halves 
of the body, there being as many as one hundred in the middle 
1 Vejdovsky, Z.c., Taf. III, Fig. 17. 
2 Harriet Randolph, /enaische Zeit. f. Naturg., Bd. XXVII, n.F. XX, pp. 463- 
476. 
3 Vejdovsky, Z.c., p. 98. 
* Gustav Eisen, Pacific Coast Oligochaeta, II, Cal. Acad. Scz., Vol. II, No. 5: 
Pl. XLVII, Fig 20. 
° Fanny E. Langdon, The Sense Organs of Lumbricus agricola, Journ. of Morph., 
Vol. XI, pp. 193-234. 
° R. Hesse, Zur vergleichenden Anatomie der Oligochaeten, Zeit. f. wiss. Zool., 
Bd. LVIII. 
