NOTES AND MEMORANDA. 
299 
simple addition, however, serves to remedy this defect, and makes the 
most convenient frog-plate we have ever used. A plain under-plate is 
riveted to the ordinary notched (upper) plate at one end with a strip 
between them, which holds them a little more than an eighth of an 
inch apart. The lower plate (which has a hole which corresponds 
with that in the upper one) passes under the clips of the stage, which 
retain it securely, but allow proper freedom of motion.* 
Variation in Spongilla fluviatilis. — Mr. J. G. Waller details, in 
No. 37 of the ‘ Quekett Club Journal,’ the result of examinations which 
he has made on various specimens of Spongilla, principally from 
different parts of the Thames. He shows that it is subject to con- 
siderable variation, but from the easy manner in which the changes 
seem to pass through a series of gradations to a complete development 
of parts, and notwithstanding the remarkable differences between the 
two extremes (the smooth spicule of the type yielding place to the 
spinous one and becoming practically obsolete), he considers that, 
undoubtedly, S. Meyeni and S. Parjitti should be treated as varieties 
only, and not as distinct species. Mr. Waller considers that S. flu- 
viatilis may be divided into two natural divisions, one having the 
spicule smooth and the other spinous. 
Borax in Vegetable Physiology. — If we immerse in a cold aqueous 
solution of borax (from 5 to 6 per cent.) vegetable organs containing 
different colouring matters, the red, blue, purple, or violet liquid 
matters diffuse themselves rapidly in the solution, whilst the green 
pigment of the grains of chlorophyll is not diffused. We can in 
this manner show the presence of chlorophyll in plants in which it 
is completely masked by other colouring matters, for example, in the 
red variety of Atriplex liortensis, in Simodurum ahortivum, in certain 
red and yellow Algse, &c. A little unicellular Alga, which produces 
blood-coloured stains on damp vaults, the Porphyridium cruentum, 
Naeg., has been placed by Rabenhorst among the Phodophycece, Algaa 
which are distinguished from others by the absence of chlorophyll, 
and by the presence of a generally red colouring matter. But it is 
sufficient to immerse this little Alga for a few hours only in a solution 
of borax, in order to see the whole of the red matter disappear ; the 
plant then becomes completely green under the influence of the true 
finely-divided chlorophyll. | 
The Vernier applied to the Microscope. — American opticians have 
recently applied the vernier to the body of the microscope (in which 
they are being followed by English makers), and some controversy 
has taken place in the States as to who was the “first and true 
inventor.” A propos of this controversy M. Bauwens, the Treasurer 
of the Belgian Society of Microscopy, communicated a paper to the 
Society on the subject, from which the following extracts are made : — 
“It is about ten years since I applied the vernier to my Jackson- 
Lister instrument, the scale being applied to the movable body, and 
* ‘ American Journal of Microscopy,’ vol. iii. p. 158. 
t M. Schnetzler, in ‘Comptes Rendiis,’ vol. Ixxxvii. p. 381. 
Y 2 
