70 Rhodora [APRIL 
Characium cylindricum n. sp. Cellula 24—430 longa, 10-20 и diam., 
cylindrica, apice rotundata, basi in stipitem brevem attenuata; disco 
basali nullo. 
Cell 24-430 » long, 10-20 н diam., cylindrical, with rounded apex, 
base tapering into a short stipe, without basal disc. — On the minute, 
crustacean, Branchipus vernalis, Medford, Massachusetts, May, 1903, 
1904, 1905 and 1906. 
Characium cylindricum, in the one cell stage (figs. 10, 11, 12 and 13, 
pl. 79), has a central nucleus and two parietal chromatophores. ‘The 
chromatophores almost completely line the circumference of the 
cell, are slightly but distinctly separated from each other, thus afford- 
ing a good view of the nucleus, situated near the middle of the cell 
and are without pyrenoids. Numerous small oil globules are often 
present in the cell. ‘The lower portion of the cell tapers into a very 
short stipe with base rounded or pointed and often slightly bent at the 
place of attachment to the substratum. 
Characium cylindricum occurs in greatest numbers upon the margi- 
nal hairs (on both main shaft and small branches) of the appendages 
of Branchipus vernalis, but may occur anywhere on the appendages. 
Each individual is attached by means of a small, brownish, muci- 
laginous mass, distinct in outline, and usually very conspicuous on 
account of the detritus present upon its surface. See fig. 25 (pl. 79). 
The transparency of the chitinous wall of the hair affords an excellent 
opportunity to study the attachment from any point of view. In fig. 
25 (pl. 79) the cell (a) is attached to the under side of the hair. The 
adhesive substance, when circular in outline, might easily be mis- 
taken for a disc, did not its transparency permit a clear view of the 
pointed or rounded outline of the wall at the base of the cell. When- 
ever the cell is attached to two or more of the smaller hairs, they 
incline toward a common point of crossing, at which point the muci- 
laginous substance adheres. ‘This method of attachment seems 
quite as well adapted to its function as do the rhizoids of Characium 
gracilipes. When Characium cylindricum cells. become detached 
from the hairs by mechanical disturbance of the cover glass, the adhe- 
sive substance usually sticks to the substratum, and the basal ends of 
the cells are clean, as illustrated in figs. 1, 2, 7, 8, 10, 11, 12, 13, and 24 
(pl. 79). Observations under conditions of minimum mechanical 
disturbance show small patches of the adhesive substance here and 
there on the hairs, thus indicating that the cells of Characium cylindri- 
cum occasionally become detached from the live Branchipus. 
