140 FORMATION OF SHELLS OF ANIMALS, ETC., 
covering its respective hemisphere, and converging towards 
its pole, near to which the fibres appear to dip into the 
substance of the lens, and insensibly to blend with the 
nucleus. Now, to obtain the best view of these fibres, 
and the manner in which they are formed, the lens, whilst 
being examined, must be placed with either its anterior 
or posterior surface towards the observer, and with its 
polar axis corresponding to that of the microscope. In a 
few seconds after the lens, still enveloped by its capsule, 
has been in the water, the latter will become visibly in- 
creased in size, and a space will begin to appear around 
the edge of the lens, between it and the inner surface of 
the investing capsule. The lens itself will also become 
enlarged, and continue enlarging, so long as it is acted 
upon by the water, until its capsule, becoming incapable 
of further distension, will burst, and the lens will be either 
entirely or partially extruded. The time which will 
elapse after the contact of these parts with the water 
before this takes place, will depend upon the age of the 
fish from which the eye was taken, varying from two 
minutes in a very young fish, to five in an older one. It 
is at once obvious, that this distension of the capsule, and 
enlargement of the lens under these conditions, is the 
effect of endosmose. If the examination is made before 
any distension has had time to take place, clear, more 
or less compressed globular particles of an oily-looking 
fluid, and of very various sizes, will be seen through the 
capsule lying close to its deep surface. As the distension 
increases, a clear space around the margin of the lens, 
between it and the capsule, comes into view, and the 
before-named oily looking particles becomes more distinct, 
having increased in size, and apparently in number. They 
still present no kind of regularity either in shape, size, 
