422 Notice of some Aquatic Worms of the Family Naides. (June, 
from two to four individuals together. From the want, in many 
cases, of sufficiently complete descriptions and accurate represen- 
tations of the European forms, there is more or less’ uncertainty 
how far ours may agree with or differ from them. 
Among our Naides I have observed several species pertaining 
to or nearly allied with the singular genus Dero. One of these, 
formerly described under the name of Dero limosa (Proc. Acad. 
Nat. Sci., 1857, 226), appears to accord so closely with the Euro- 
pean species, Dero digitata of Oken, that better means of com- 
parison may prove it to be the same. The latter, originally 
described and figured by Miller upwards of a century ago, “as 
the blind Naiad ”—“ die blinde Naide” (Von Wirmen, Kopen- 
hagen, 1771, 90, 95, Tab. v, Fig. 1-3) is represented with the 
body of the worm ending in a broad funnel-like pavilion opening 
obliquely upward and furnished with four pairs of divergent 
rays, successively increasing in length from before backward. 
Another European species, described by Udekem as Dero obtusa, 
is represented with two pairs of rays to the caudal pavilion (Bul. 
Acad. Sci. Belgique, 1855, 549; Mem. Acad., 1859, 18), and is 
likewise so described by Perrier (Archiv. Zool. Exp., Paris, 1872, 
65). Semper has more recently described two species, Dero 
vodriguesii and D. philippinensis, which differ from the preceding 
and each other in the character of the caudal pavilion (Arbeit. 
Zool. Inst., Wurzburg, 1877, 106, 107). 
Dero limosa is frequent, and is to be found creeping among 
aquatic plants or on the sides of the vessel containing the water 
in which they have been collected, or it may be observed partly 
buried in sediment, projecting from a short chimney of its own 
construction, rising above the surface of the sediment, and with 
the caudal pavilion expanded. 
The characters of the worm are as follows: Body compressed 
cylindrical, transparent, with red blood. In an individual of a 
fourth of an inch in length, without signs of division, there were 
forty-eight rings, or body segments, of which about, a dozen pos- 
teriorly became successively more and more rudimental in the = 
disappearance of the podal stylets and bristles. In specimens — 
exhibiting evidence of division into a series of from two to four 
individuals, measuring up to half an inch in length, and stretch- 
ing even to three-fourths of an inch or more, the number of 
rings together did not appear to be greater, and sometimes was 
