268 
MEMORANDA. 
It is not attempted to be inferred that so simple an in- 
strument as I have described is intended to supersede the use 
of the mechanical stage when the microscope is furnished 
' with one, but, in its absence, and then only, I offer it to every 
observer to whom economy is an object, as a substitute for 
the " sliding rest'' usually supplied to " Warington's" and 
other cheap forms of microscope. 
The advantages proposed by Mr. Busk are — 1st, thinness 
of stage, — mine is exactly one-eighth of an inch ; 2d, steadi- 
ness of motion, — mine has equal advantage ; and 3d, its 
trifling cost, — mine cost me eighteen-pence, item, one shilling 
for the magnet and sixpence for the wooden stage. From 
inquiries I have made, I am led to believe that Mr. Salmon, 
of Fenchurch Street (who furnished the Warington's''), 
could supply the magnetic stage in brass, instead of wood, at 
the same price as the present " sliding rest.'' 
I shall be happy to show the instrument to any reader who 
may take an interest in the subject. — J. Newton Tomkins, 
F.E.C.S., Kussell Place, London. 
Facts on the Propagation of Actinia. — My aquarium affords 
at this moment a curious illustration of a mode of increase 
in a beautiful specimen of A. dianthus, which I do not re- 
member to have seen noticed. Although special reproductive 
organs are well known to exist in the Actiniae, it would 
appear that they are not actually necessary to the multipli- 
cation and continuation of the species, as this end can be as 
easily accomplished, and with as much certainty, by fissuration 
and self-multiplication. I have lately had an opportunity of 
witnessing both processes, in white specimens of A. dianthus. 
In one, a fully formed offset was thrown out about half an 
inch from the foot ; this continued to grow for some weeks, 
and was ultimately thrown off, having attained a considerable 
size. In another instance, the animal became so firmly ad- 
herent to the side of the glass, that, after having vainly en- 
deavoured to detach itself, with an apparent degree of violence, 
it positively tore itself away, leaving behind six small pieces 
of the outer margin of the circular foot. Firmly glued to the 
side, these portions served for many days merely to mark 
the spot ; at the end of a week I took a piece of stick, and 
was about to clean them off, when, much to my surprise, I 
saw that they retracted as soon as I touched them : in a few 
days more, I was stiU more surprised to see a row of tentacles 
round the head of each ; and they have at this time consider- 
ably increased in size, so that my stock is richer by six 
perfectly formed Actiniae. The parent certainly suffered at 
