MEMORANDA. 307 



using the l-12th I can Avithout difficulty move an object on 

 the stage l-130,000th of an inch. I beg to introduce to Mr. 

 Ross all who desire this convenience and not superfluity. — 

 J. Mitchell, Captain European Veterans, Madras Museum; 

 June 20th, 18G2. 



Polycistina off the Orkneys. — I beg to mention the fact that 

 I have found some Polycistina in sand dredged by Messrs. 

 Waller, Gwyn Jeffreys, and Norman, oflP the Orkneys, in 

 July, 1861, Lat. 60° 30' N., long. 0° to 1° E. They are 

 very rare, only nine specimens occurring in fifty slides ex- 

 amined with great care. Still, as I have never mounted any 

 Polycistina, their presence cannot be attributed to any other 

 source, and I am forced to conclude that they come from the 

 locality which I have mentioned, although it is north of their 

 pre^dous supposed habitat. — T. G. Stokes ; August 21st, 

 1862. 



Highley's New Compressorium. — All the forms of compres- 

 sorium I am acquainted with seem to have been designed by 

 the philosophical instrument maker, rather than the anatomist 

 conversant with the practical requirements of microscopical 

 manipulation, for the space placed at the disposal of the 

 operator is far too limited. If the object subjected to com- 

 pression be only microscopic, such instruments may serve their 

 pui'pose. The compressorium, however, is generally used by 

 the anatomist to assist in tracing out parts in objects of some 

 magnitude. If, for instance, we wished to follow the anatomy 

 of an annelid placed on a glass slide, three inches by one inch 

 or longer, we should have some difficulty in bringing all the 

 parts under the compressor; for to do so, we should have 

 to reverse the ends of the slide ; and in all the instruments I 

 have handled, the centre of the slide cannot be placed conve- 

 niently in position. To obviate this imperfection in the 

 instruments at present in use, I have arranged a compres- 

 sorium which meets every requirement, whether for micro- 

 scopic or larger specimens, animal, vegetable, or pathological. 



The arrangement will be readily understood by aid of the 

 the annexed illustration. A base-plate for the support of an 

 ordinary 3 inch by 1 inch glass slide is placed at right angles 

 to a projecting portion that carries the arm and mechanism 

 of "the compressor ;^^ in front of the base-plate, a ledge is 

 placed, against which the glass slide can firmly rest, as sug- 

 gested by my friend. Dr. Lionel Beale (see illustrations to 

 ' How to Work with the Microscope,^ xviii, fig. 80). In the 

 centre of the base-plate is an aperture with a sunk ledge, into 

 which a disc of thin glass can be dropped when required for 

 examining both sides of an object. The compressing ring, 



