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rangement enables me to throw the beam on the object at all 
_ angles of incidence, whether from beneath, as in the case of 
translucent, or from above, in the case of opaque objects, and 
as the sector is graduated, I have the power of observing and 
restoring any position at pleasure. 
‘To fulfil the second condition, the stage of the micro- 
scope is made to revolve round the optical axis, and in a plane 
perpendicular to it. This is effected by constructing the stage 
on entirely a new plan, in which the slow motions are obtained 
from concentric rings forming a part of the stage itself, and 
equally available in every position ofthe latter. By this ar- 
rangement the beam of light may be thrown on an object in 
any azimuth, and a suitable graduation of the stage enables 
the observer to register and restore its position at any time. 
“ Hereafter,” continued Mr. Grubb, “I hope to lay be- 
fore the Academy some of the results obtained by the use of 
these arrangements; at present I shall conclude by observing 
that they are ofa highly interesting character, and likely to 
lead to important discoveries.” 
Dr. Allman presented to the Academy the results of some 
_ unfinished observations he is at present engaged in on the 
_ Clayiform and Sertularian Zoophytes. He has found that the 
_ medusoid structure, hitherto supposed to be confined to the free 
locomotive gemmz of these animals, exists also in the fixed 
 oyvisacs, though generally so far disguised as to render it easily 
_ overlooked. This structure he has found in Coryne, Synco- 
__ ryne, Tubularia, Cordylophora, and Sertularia; and he believed 
himself justified in generalizing the observed facts into the pro- 
position that a medusoid structure in some form is necessary 
in these zoophytes for the production of true ova. 
