218 Transactions of the Royal Microscopical Society. 
oesophagus : that stream is further scrutinized by the two lovely little 
lip-like organs situate just over the mastax, which touch each particle 
so lightly and rapidly and admit or reject it as they approve or 
disapprove of it ; it is astonishing to see how the little quick jerk 
which they give tosses an objectionable morsel up into the central 
stream of waste and drives it away, thereby actually making a sixth 
separate and distinct stream in this minute space. These two 
organs are represented conventionally in the diagram by two 
triangles, while the mastax (also represented conventionally), lies 
just below them. Now it sometimes happens that the two 
janitors above and the cushion overhead have not done their 
duty, and that in spite of their vigilance an unwelcome and 
unsuitable intruder of unusual magnitude has reached the more 
delicate tasting organs below ; the jerk that was sufficient for an 
ordinary sized particle has no effect upon this one, it is sent up 
only to return, and this happens over and over again until the 
sinus gets clogged up with matter — the little lips are so occupied 
in jerking up that they let nothing pass down, and the result is a 
stoppage of all food. Now there is but one thing to be done, 
and that is to stop the stream from above, for as long as it goes 
pouring on, the downflow will beat the upthrow, and the objection- 
able particle will not leave the sinus ; but in order to stop the stream 
from above, the main wheel itself must stop — and so it does, the 
row of cilia round the edge of the lobes stops dead, the downflow 
stops, the mastax joins the little lips in the jerk up, as if determined 
to have no more trifling, and throws the particle out, and there- 
upon everything goes on again as before. It is curious to observe 
here that when the main wheel stops it “ holds its attitude,” the 
cogs are there, but motionless. All the cilia remain in statu quo, 
and you have the same effect as that so beautifully represented by 
Mr. Cubitt in his drawings of Stephanoceros,* showing, if anything 
were wanted to prove it, that the motion of the cilia is exactly the 
same as that of the stalks of corn in a field under a passing breeze, 
where each separate stalk moves in succession and rhythmically, 
but each stalk is a little after its neighbour on one side and 
before its neighbour on the other. 
The construction of the pellet in the pellet organ itself is the 
next point that calls for our attention : this organ is so well 
known that it is sufficient to describe it as of a cup shape, 
situate under the main chin, and full of cilia, the mouth of 
the cup being placed perpendicularly, so that when the animal 
is upright the medial axis of the cup is horizontal ; here I agree 
with Mr. Cubitt that the “ normal ” shape of the pellet when 
made is that of a Minie rifle bullet, as in Fig. 5. It is to 
this faff that I think Mr. Slack refers in ‘ Pond Life,’ p. 93, 
* ‘ M. M. J.,’ vol. iii. p. 248. 
