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tory transverse section the spermatophor must be imbedded 
in wax and oil, and cut with the razor. A section so obtained 
is drawn in fig. 7. The same layers are seen as in fig. 4, but 
it is observed that the filaments (spermatozoa) visible in the 
striated layer have an imbricated, curved arrangement. This 
is important, as it helps to explain the way in which the 
spermatozoa have been felted together. The section represents 
the proximal portion, that is, the portion nearer the conical 
head, and it indicates that the sperm-rope has been twisted 
from right to left (on its own axis), by which means the 
curved, imbricated radiation has been produced. 
If we now examine the structure of the sperm-rope from 
the surface downwards, we find the following structure. In 
a living specimen from TZ. rivulorwm the surface is often, 
but not always, seen to be in a state of active vibration. 
With a high power (No. 10 4 immersion, Hartnack) the 
vibratory surface presents the appearance drawn in fig. 2, 
when in active movement. The moving bodies are the 
vibratile filaments of the spermatozoa, three of which, isolated 
and greatly enlarged, are seen in fig. 6. The reflected 
portion forming a loop is the filament of the spermatozoa. 
In T. rivulorum, as before observed, the projecting portion of 
the filament is short, but in 7. wmbellifer, and other 
Seenuride, it is of considerable length, and gives rise to most 
active locomotion of a very graceful kind, and strongly re- 
sembling that of the ciliated Infusoria. This is a very 
remarkable phenomenon, and calculated to throw some light 
on the nature of ciliary movement, when we remember that 
each of the vibrating elements here cemented together, has 
had an independent development, and is in no kind of organic 
connection with its neighbour, and yet the vibration of the 
whole surface proceeds with as much regularity and results 
in as definite a locomotion as in the case of Infusoria whose 
cilia are presumably in organic connection, and, therefore, 
possibly under some central control. We might have 
expected in these spermatophors irregular spasmodic vibrations 
of the component spermatozoa, the one acting so as to 
neutralise the other, but instead of this we obtain a perfect 
and regular ‘‘ wave” of vibration, which resembles that seen 
on any ciliated membrane. This fact proves, firstly, an 
actual identity between cilia and the filaments of spermatozoa, 
and secondly, that the co-ordination of ciliary movement is 
independent of any common organic connection of the cilia. 
Leaving, for the present, the physiological questions here 
raised, we pass below the vibrating surface of the sperm-rope, 
and find a striated structure indicating the spiral arrange- 
