"jSS. aLT{T86?J ^ ^riiall Zoophyte Trough. 239 
changes they are prone to undergo. How far the absence of a dis- 
tinctly defined " nucleus " after death depends on their smaller size, 
I am not prepared to say. 
Many questions of course follow. For example, how far is 
this separation of the substance of a homogeneous * corpuscle into 
nucleus, cell-membrane, and contents, to be compared to the coagu- 
lation of the blood ? and how do the agents, which are known to 
influence the one process, affect the other ? A still further and 
more important question is, How are these changes in the cor- 
puscles, and in the blood around them, related ? But in this paper 
I propose to go no further than the statement that the red corpuscle 
of all vertebrata is, in its natural state, structureless. When living, 
no distinction of parts can be recognized ; and the existence of a 
nucleus in the red corpuscles of ovipara is due to changes after 
death, or removal from the vessels. 
I cannot conclude this paper without acknowledging the great 
help I have received in this investigation from Mr. Howard Marsh, 
Demonstrator of Microscopical Anatomy at St. Bartholomew's Hos- 
pital. — Paper read he/ore the Royal Society, March 18th. 
X. — A Small Zoophyte Trough. By W. P. Marshall, President 
of the Birmingham Natural History and Microscopical Society. 
In the examination, under the microscope, of small living aquatic 
objects, animal or vegetable, such as larvae, or desmids, &c., the 
want has been felt of a very small open glass trough, small enough 
in diameter and depth to limit the motion of the object within the 
range of a low-power objective, without requiring alteration of the 
stage or the focus, and allowing of black-ground illumination by 
the parabolic condenser ; whilst at the same time retaining the ad- 
vantages of the ordinary zoophyte trough for observing objects in 
a natural, free condition, and affording the means of removing the 
water and reaching the object whilst under the microscope, with a 
curved needle or fine brush. The following is a description of a 
simple and convenient little trough that I have contrived for this 
purpose, and it has been found very useful and satisfactory in work. 
An ordinary cell of glass, ebonite, or other material, cemented 
upon a glass slide with marine glue, has a half cover-glass fixed on 
with asphalte varnish, and made out of an ordinary round cover- 
glass cut in half across tlie centre. A semicircular open trough is 
* By the word homogeneous I do not mean to affirm that the substance of the 
corpuscle is of equal consistence througliout. The central may be the softest part 
of it. But I regard the corpuscle, in its whole substance, as " having the same 
nature." 
