No. 419.] A PARASITIC OLIGOCHETE. 909 
3 and 4; f, one like e, but with a deep groove formed between 
the two sets of developing setae. 
Before the bud breaks away from the parent, a new individ- 
ual has begun to develop between the two. In my experience, 
which has extended over only a single month, it has been rare 
to find a chain consisting of more than three persons, and as in 
such chains the older bud is often so far developed as to be 
readily detached from the rest by the pressure of the cover, I 
am inclined to doubt whether colonies of as many as sixteen 
zoóids (cf. Claus, Warzburger naturwissenschaftliche Zeitschrift, 
Bd. I, pp. 37-40, 1860) are ever found in our form. 
Upon comparing this description with that given by Lan- 
kester for the European form, it will be seen that the only 
important difference which has been shown to exist relates 
to the number and arrangement of the setze in the different 
bundles. I am uncertain how much importance should be 
attached to this difference. Lankester describes his species 
as having twelve setæ in the cephalic bundles and eight in the 
abdominal ones, and after having for more than three years 
“taken every opportunity of examining the little worms " 
states that this number is ** almost invariable” (Quart. Journ. 
Micr. Sci, N.S., Vol. IX, pp. 272, 279). Vejdovsky, on the 
other hand (System und Morphol. d. Oligochaeten, p. 36), in 
describing the same species, says : “ Bezüglich der Anzahl der 
Borsten variieren die Bündel bedeutend, indem man auf den 
hinteren Segmenten gewöhnlich eine gróssere Menge derselben 
vorfindet als in den vorderen Borstenbündeln. Im allgemeinen 
trifft man in einzelnen Bündeln, 8, 9, 10, 10-12 Borsten." I 
have not, however, in an incomplete but somewhat careful 
review of the literature, been able to find published authority 
for this statement of Vejdovsky. - 
In view of this uncertainty and of the fact that edi tip s 
paper, which contains the only full anatomical description of the 
European species, is somewhat difficult of access, it has seemed 
worth while to give a fairly full account of our own torm. - 
nd so admirable that it has not 
kester’s plates are so complete a hat 
ions to this description- 
seemed desirable to add illustrat 
ZOÖLOGICAL LABORATORY, WELLESLEY COLLEGE. 
