182 Transactions of the Boy at Microscopical Society. 
inspection of Figs. 8, 9, and 10. These are imaginary transverse 
sections across the mastax, and they show how, as an upward force 
is applied to the alulm at c (the points of the teeth being kept 
together), the free edge of the central blade must gradually work 
upwards, and the points of the teeth which are rigidly connected 
with it must come down. 
Passing now to the manuhria^ we find that they also are sources 
of very active power, and though they cannot turn the points of the 
teeth down, yet they give a sharp push, almost like an impatient 
blow, longitudinally along the teeth from behind, and thus tend to 
grind more closely against each other the surface ridges of the teeth, 
already bent by the aluldc into a bowed form. This same push of 
the manubria, indeed, has sometimes a most remarkable effect, for 
I have witnessed it when it has come too soon, and has therefore 
actually bent the teeth the wrong way ! This is shown in Fig. 11, 
where the depression in the centre of the teeth and on each side 
at (]j) is due to the fact that at the moment in question the alulae 
were not being lifted up, and as the force proceeding from the 
manuhria thus acted in a perfectly straight direction, it met with 
a reaction, because the teeth were point to point, and so the teeth 
curved the wrong way ; and thus abnormally the very contingency 
arose, which by introduction of the power at the end of the alulse 
is as a rule prevented. I may add that Mr. Gosse has already 
dealt with the action of the manuhria in other rotifers {1. c.). 
Now I do not know how it may strike others, but to me this 
mechanism is simply exquisite. We have three distinct lines of 
power; all at work and in rotation. In the first place there is a 
power at hinge K, then follows the power at hinge H, and then 
lastly comes that of the manuhria ; the moment the main upper 
handles of the ramus get together, then, and not before, up go the 
alulm and down go the points of the teeth ; the slightest touch does 
^ it, and then the manuhria come in from behind with their crushing 
force. The hinge H possesses a very distinct power of gaping 
widely open to take in a large body, and the hinge K shares this 
power, though hardly, I think, to the same extent. As a whol,e I 
should describe the organ as a marvellous machine, exceedingly eco- 
nomical of power, and arriving at the best results with very simple 
and delightfully ingenious means. I am unable to identify any 
particular muscles — indeed I doubt their existence as separate 
cord-like attachments — I only saw the movements of the parts, 
but not what produced those movements ; my belief is, that 
the spherical bodies which support and enclose the principal parts 
are themselves highly sensitive and contractile. 
The examination of the living Conochilus thus quite confirms 
me in the a priori views which I have already expressed in this 
essay as to the method in which the mastax of Melicerta obtains its 
