Building Apparatus of M. r ingens. Bg F. A. Bed-well. 217 
see ; but over each of these side rows of cilia I make the wall of 
the sinus “curl” so as to represent the edge of an ordinary 
flat sponge bath when turned inwards, and thus when once a 
particle sets off to a side chin, this overhanging “ eave ” acts as a 
covered way and prevents it flying upwards and joining the stream 
above it, and protects it from the effects of the rush of that stream ; 
for this is most noticeable, and a point easily verified — namely, that 
the passage of each set of mural fragments to its own' side chin is 
comparatively slow and regular relatively to the rush of waste above, 
and that the contrast between the rate of each stream is marked 
and distinct, and has to be accounted for. 
I have not attempted in the diagram to give the effect here 
referred to, it would tend to confuse the parts, but the ocular 
impressions from which I deduce the existence of the last- 
mentioned arrangement, are as follows : — If the animal is stand- 
ing sideways, then as we focus downwards the moment we arrive 
at the nearest mural stream, made visible by carmine, and get 
it in “ true view,” we shall find just over it the edge of the cor- 
responding protecting and projecting “ eave ” : focussing onward we 
shall pass through the central stream of “ waste ” and reach the 
other mural stream, and just before we reach it and above it is 
the edge of the accompanying eave ; on the other hand, if we 
take the animal transversely, and suppose that we are looking over 
the main chin and right into the pellet organ, now as we focus 
down we meet the particles as they bounce up from the cushion to 
the side chins and to waste, and then focussing on we shall 
get a successive series of outlines in “ true focus,” forming re- 
peated transverse sections of the sinus, and if I am right they 
will appear as in Fig. 4, where Fig. e is the section nearest 
the eye, and represents the end of the main chin with the side 
ditches to the pellet organ, while Fig. a is the section farthest 
from the eye and close to the cushion. Now all these particulars I 
have seen — and I had once the privilege of seeing and studying 
M. ringens with its lobes turned flat towards me, so that I could 
look right over the main chin and into the pellet organ — and 
Fig. 4, a, b, e, d, e, represent the actual effects produced on the 
eye in focussing from above and downwards on that occasion* 
Keturning to the cushion, we must follow for a moment (and 
before we go on to the pellet organ itself) the stream that goes to the 
* Mr. Cubitt has used words which lead mo to conjecture that lie has seen the 
effects here insisted on. for at p. 200, vol. v. of the ‘ M. M. J.,’ he says, speaking 
of the mural streams, that he has seen them ‘‘ course along the chases beneath the 
lateral margin of the dorsal lobe.” The word “beneath ” here exactly expresses 
what I describe. I am bound to add, however, that I have never been able to 
persuade my friend Dr. C. T. Hudson that my observations are correct, and as 
long as such an observer differs from me I cannot but fetd somewhat anxious as 
to the accuracy of my conclusions. 
