REDFERN, ON FLUSTRELLA HISPIDA. 97 
in a semicircle over the summit of the cells, in the specimens 
from Dublin, Wicklow, and North Wales. 
In the Kincardineshire specimens, the young cells have 
five to seven or nine hairs in a semicircle over their summits, 
and two or three only on each side. The older cells have 
hairs distributed uniformly over their whole circumference, 
their lateral septa often presenting eight to twelve or more 
hairs with their roots closely packed together, one half 
haying their points directed over the cell to the right of the 
group, the other half having theirs turned over that to its 
left. One of the lateral hairs on each side often reaches 
across the cell at the lower margin of its aperture, but no 
hair of any kind grows in any other position than those above 
indicated.* 
In the specimens from the Irish and Welsh coasts, the 
summit of the cell has often no more than three hairs upon 
it, the usual number being five to seven; the sides and base 
of the cells are often entirely devoid of hairs, the lateral 
septa occasionally presenting a patch of two or three. So 
far as I am able to judge from the examination of a large 
number of specimens, there is always a wide difference in the 
number of hairs on the Kincardineshire specimens and those 
gathered further south, this difference being the more re- 
markable, because an inverse ratio maintains between the 
number of hairs and the extent of the coencecium in the two 
series of specimens. JI am anxious that the attention of 
naturalists should be directed to this occurrence, because it is 
possible that the functions of the hairs may be determined 
by observations of the number and character of the hairs of 
the same species, growing under different circumstances. 
The aperture of the cell is somewhat quadrangular—dis- 
tinctly so during the protrusion of the polypide. The charac- 
ters of the cells, their hair sand apertures, are shown in Pl. 
IV, figs. 1, 2, 3, and 3 dis.+ 
The polypide, when healthy, is easily removed from the 
cell with its digestive viscera entire, as in fig. 4. The number 
of tentacles I found to be twenty-eight in all but one of a 
large number of instances, in which I counted them with 
* Tn old and mech imbricated specimens the hairs on the sides and base 
of the cells are best shown by slicing the ccencecium from the plant, and 
dissecting the cells asunder by needles. By this method the polypide may 
also be easily removed from its cell in so perfect a state that it will live for 
many hours, showing the effects of ciliary motion more beautifully perhaps 
than in any other instance whatever. : hed. ; 
+ The subsequent observations were all made on Kincardineshire speci- 
mens. 
