66 Rhodora [APRIL 
Branchipus were collected that spring; in the spring of 1904 a few 
more were collected from the same pond; but not until the spring of 
1905, however, were conditions favorable for collecting the material 
in sufficient quantity for the P. B.-A. sets. At that time there was 
but little water in the pool, and it lowered so rapidly during the time 
Branchipus was present, that the animal was driven gradually toward 
deeper water. I was able to scoop up with a net from the muddy 
hole in the middle of the pool, about a pint of specimens, which I 
preserved in 5 % formaldehyde. Other pools in the vicinity were 
frequently but unsuccessfully examined. Only the one pool con- 
tained it, and in such abundance that а recent examination of the 
material collected in 1905 showed the Characia attached not only to 
Branchipus, but also to mosquito larvae, which had been overlooked 
at the time of collection. In May, 1906, a few sketches, not more than 
eight or ten, were made from a small number of specimens collected 
at that time, but the scarcity of. Branchipus made it advisable to 
postpone further investigations until the next spring, when, it was 
hoped, material would be sufficiently abundant for a study of the 
reproduction. Failure to find the material in 1907 and in 1908 leads 
me to fear that it may have disappeared entirely; hence the publica- 
tion of the present account founded almost wholly on material which 
was collected їп 1905 and preserved in formalin, and from which sets 
for the P. B.-A. were prepared." | 
Characium graeilipes occurs in greatest abundance on the flat 
surfaces of the two sides of the abdominal appendages of Branchipus, 
and rarely on the marginal hairs for which Characium cylindricum 
seems to show a preference. Both species, however, may be found on 
the head, antennae, and mouth-parts, and dorsal surface of body and 
tail. In respect to size, both Characium gracilipes and Characium 
cylindricum differ greatly from all species heretofore described: the 
smallest specimen of Characium gracilipes which I measured, 80 y, 
was almost as long as the extreme length given by West? for Chara- 
cium ensijorme Herm, 86 s, which, he states, “is the most elongate 
species of the genus." The longest specimen of Characium gracilipes 
! In order to prepare the material for the P.B.-A., about 500 formalin specimens of 
Branchipus were spread out to dry on a clean sheet of glass, When dry, they were 
fastened on mica with glue, two or three specimens on a piece,  Characium gracilipes 
P. B.-A., №, 1270; Characium cylindricum P. B.—A., No. 1269. 
2 West, G. S. The British Freshwater Algae, Cambridge, 1904, p. 200. 
