NOTES AND MEMORANDA. 
To the Editors of the Quarterly Journal of Microscopical 
Science. 
Srir,—In the account of the discovery of the segmental 
organs in Elasmobranchs by Professor Semper, and myself, 
which appeared in the January number of your journal, one 
or two expressions are used, which might lead to an erroneous 
impression as to the priority of this discovery. This rests 
with Professor Semper, who published his first note on the 
subject in July, my own account, though entirely inde- 
pendent of his, not being published till October. 
F,. M. Batrour. 
[What we said was that Mr Balfour was the first to publish 
figures establishing the fact of the existence of a series of 
openings into the body-cavity from the primitive kidney-duct 
of the Elasmobranchs. This, we believe, is true.|—Eps. 
Amplifiers for the Microscope——In the Biological and Mi- 
croscopical Section of the Academy of Natural Sciences, of 
Philadelphia, January 4, 1875, Dr. J. Gibbons Hunt made 
a communication upon the subject of amplifiers for the mi- 
croscope, in the course of which he remarked that from the 
time of the first observation by the aid of more than two 
conyex lenses, an almost constant effort had been made by 
opticians to fit in the best intermediate glasses, and yet 
further improvement in this respect was confidently to be 
looked for. ‘The amplifier which he had upon the table 
consisted of a concavo-conyex lens, with its concave side 
turned towards the eye, and so placed within the body of 
the microscope as to stand at a considerable distance from the 
objective. This adjustment of position was best accom- 
plished by having the amplifier screwed to the end of a tube 
arranged with rack-work in such a manner as to traverse 
six or eight inches, because we could thus compensate for a 
want of complete correction in the objectives employed. 
The advantages obtained by using an amplifier were, in 
the first place, gain in magnifying power, as could be seen in 
his microscope upon the table, when with an amplification of 
800 diameters, afforded by a four-tenth of an inch objective, 
