NOTES AND MEMORANDA. 
213 
The sections will then stand thus : — 
I. Discida. — Mostly discoidal, sometimes elliptical, rarely cylin- 
drical or spheroidal. Skeleton in part intracapsular, and consisting 
always of both circumferential and radial parts, which may be quite 
irregularly disposed, but which properly form an external, perforated 
shell, with an internal partition or spheroidal mass, forming a series 
of mutually communicating chambers, which are either concentrically 
or spirally arranged. No flagellum. Growth, multipolar or centri- 
fugal. No nuclear vesicle. 
II. Flagellifera. — With a flagellum. No nuclear vesicle. 
III. Entosph^rida. — With an intracapsular spheroidal shell; 
not traversed by radii. No nuclear vesicle. 
IV. Acanthometrida. — With radial skeleton, the radii of which 
meet in the centre of the capsule, and consisting more or less of 
acanthin. No nuclear vesicle. Yellow cells generally absent. 
V. PoLYCYSTiNA. — Simple, ectolithic forms, with more or less 
compact skeletons, often with unipolar growth. No nuclear vesicle. 
VI. CoLLOZOA. — Simple or compound. If single, then with the 
skeleton in the form of circumferential detached specula only. No 
nuclear vesicle. 
VII. Vesiculata. — With a nuclear vesicle. 
Oblique Light for Photo-micrography. — In a letter written by Dr. 
Woodward to M. Deby, the Vice-President of the Belgian Micro- 
scopical Society, in September last, he describes the method he makes 
use of when it is necessary in photo-micrography to use very oblique 
light, as in the case of Nobert’s test, Amphipleura pellucida, &c. A 
pencil of parallel solar rays (reflected by the heliostat and plane mirror) 
is intercepted by the cell containing the solution of ammonio-sulphate 
of copper and a diaphragm which only allows the passage of a circular 
pencil of J inch in diameter. The light enters parallel to the optic 
axis of the microscope placed horizontally and on the same level, but 
at a lateral distance (either right or left) of 3 inches. If the light is 
intercepted by a large achromatic prism of a focal length of about 
3 inches, the desired obliquity can be obtained without difficulty. It 
is indispensable that the stage of the microscope should be very thin, 
or otherwise a false stage must be adopted like that supplied by 
Powell and Lealand. The best result is obtained when the rays are 
concentrated to a focus on the object itself. The illumination thus 
obtained is in general sufficient to produce negatives by the wet pro- 
cess up to 2500 diameters with three minutes’ exposure.* 
The Birth of a Bhizopod. — Professor Leidy has made some observa- 
tions on this subject, which he records in the ‘ Proceedings of the 
Academy of Natural Sciences of Philadelphia ’ : — 
I have long sought for the mode of multiplication of the test- 
covered Khizopods, but thus far with little success. It appears as if 
the different forms with which we meet are always mature, and rarely 
are individuals seen with the ordinary characters which distinguish 
young from adult animals. 
* ‘Bulletin rle.la Societe Beige de Microseopie,’ vol. iv. p. (11. 
