NOTES AND MEMORANDA. 
257 
added, in two hours 90 per cent, alcohol, and, later on, absolute alcohol. 
In two days all the specimens will be found to be quite hardened. 
When stained (he recommends picrocarmine in pretty weak solution, 
and soaking for several days), all the Planaria thus treated pre- 
serve their histological structure perfectly well. There is incon- 
venience in imbedding in paraffin, as in consequence of the great 
wrinkling the parenchyma of the body is torn asunder. However, 
by gradually applying turpentine in a strong solution of paraffin this 
wrinkling can be avoided. 
By this method the most delicate Planaria, as e. g. Leptoplana, 
Proceros aurantiacus, cristatus, Thysanozoon, &c., can be prepared so as 
to partly retain the colours they possessed when living.* 
“ Commercial Microscopy” — At the “ iicoles Superieures de Com- 
merce et d’lndustrie” of Kouen has been established a course of 
instruction on the application of the microscope to commercial pur- 
poses. Dr. Pennetier, the Director of the Museum of Natural History 
at Eouen, who has taken charge of the course from its commencement, 
has addressed a note to the ‘ Journal de Micrographie,’ detailing the 
objects he has had in view and the specially satisfactory results hitherto 
obtained, and urging upon the other commercial schools of the country 
that they should follow the initiative of Eouen and establish a similar 
course. Many of the pupils of the Eouen school have owed their 
admission to the large industrial establishments to the expertness in 
microscopical manipulation which they acquired under Dr. Pennetier’s 
instruction. It is intended to publish the Doctor’s lectures, which 
include not only the adulterations of food, but the recognition of the 
nature and proportion of the different kinds of fibres in partieular 
materials, the origin and quality of the hairs employed in hat making 
and the fur trade, the raw material of which any given paper is com- 
posed, the discrimination of true ivory from the substances used for 
it, and a variety of similar matters. This subject also formed the 
basis of the recent address of the President of the Quekett Micro- 
scopical Club. 
Physiology of the Contractile Vacuoles of the Infusoria. — The fol- 
lowing observations made by Professor Th. W. Engelmann are addueed 
by him as demonstrating what hitherto has only been a matter of con- 
jecture, that the contractile reservoirs of the Infusoria empty their 
contents externally on contraeting. A new Infusorium which he was 
examining (which may be called Chilodon propellensf was the size of 
a medium specimen of Chilodon cucullulusj and accords with this species 
also in the limitation of the stripes and cilia on the ventral surface, as 
also in the presence of a discharging cytostom, in the anterior third 
of the body, and a simple nucleus in conformity with it. The shape 
is, however, slender, and towards the posterior end, in whieh the 
large contractile bladder is placed, the body is more roundly turned. 
Thus an approaeh is made of the hypotriehous to the holotrichous 
type, which is interesting from a systematic point of view. 
The animal swam about with a generally constant but very 
* ‘ Zoologischer Auzeiger,’ vul. i. p. 14. 
