96 
E. W. PHILLIPS-NOTES ON THE 
Before entering into details of the structure of the Discostomata, 
I will say a few words about their history. To the late Prof. H. 
Janies Clark belongs the honour of being the first to give a definite 
record of these creatures. In June, 1866, he communicated to the 
Boston Natural History Society a detailed account of four species 
he had discovered. The Discostomata had been previously recognised 
by Ehrenberg and Stein, but they had supposed them to he minute 
species of the genus JEpistylis. Their true organisation was not 
known until Mr. W. Saville Kent, in a paper read before the 
Royal Microscopical Society in 1878, fully described the precise 
import of the remarkable collar-like membrane which characterises 
the group, although he had previously, on the 21st of June, 1877, 
read a paper relating to them before the Linnean Society. Since 
then he has devoted great attention to them, and the result has 
been that, although more than fifty species have been recorded, 
more than two-thirds of this number have been registered by this 
most indefatigable worker. 
The animalcules included in the section Elagellata-Discostomata 
may be described as exceedingly minute, very variable and change¬ 
able in form, but, in normal adult stages, of an ovate or pear-shaped 
form, having at their anterior extremity a single, long, lash-like, 
appendage, called a flagellum, which is surrounded and partially 
enclosed by an exceedingly delicate and transparent membrane, 
which rises from the base of the flagellum in the form of a funnel 
or wine-glass; this membrane, like the flagellum, is merely an 
extension of the substance of the body, and can be either contracted 
into a cylindrical form, withdrawn into the body, or extended at 
will. The area in which food can be taken into the body is limited 
to the place or part enclosed by this collar-like membrane, and 
from this part are also discharged all faecal or waste products. 
They possess a distinct nucleus, and have one or more contractile 
vesicles. They inhabit salt and fresh water. 
Without doubt the most interesting feature is the remarkable 
distinguishing membrane, from the possession of which the animal¬ 
cules are familiarly called “ collared monads.” Such is the extreme 
delicacy of this membrane that with all ordinary high magnifying 
powers it can only be seen in profile like two fine, curved hairs, 
and as such it has been delineated by Stein, De Eromental, Butschli, 
Eresenius, Carter, and other modern writers; and it can only be 
defined by the most careful and delicate adjustment of the light, 
and the employment of the power known as a - 5 Vth objective, 
giving the extraordinary linear magnification of 5000 diameters. Yet 
it must be remembered that notwithstanding this almost incompre¬ 
hensible tenuity, it is merely an extension of the substance of the 
body, and is undergoing a constant change up the outside and down 
the inside, where it enters, and is merged in the protoplasm of the 
body (there are two surfaces, inner and outer, which, as it were 
roll or glide over each other). This action (which the mind when 
remembering the excessive thinness can hardly grasp) can be seen 
with an ordinary high magnifying power, and it is by this action 
