Blood-corpuscles of A. tridactylurriy &c. By Dr, Schmidt, 69 
delicate but distinct double contour, expands, and in most cases 
assumes a more round, sometimes even irregular form (Figs. 18 
to 23). 
By a continued action of tbe water, the contour of the blood- 
corpuscles is rendered still paler, until they finally become almost 
invisible to a careless observer. By a closer examination with 
a first-class objective, however, their outlines are readily distin- 
guished in the form of a very delicate double contour. This 
examination is facilitated by the presence of the nuclei, around 
which the observer has to look for the contour of the main body of 
the corpuscle. 
It has already been mentioned that the coloured blood-corpuscles 
of the Amphiuma do not enlarge under the action of water, but, on 
the contrary, appear smaller in the dimensions of their front view. 
This diminution of size may be due to a partial or entire disso- 
lution of their protoplasm by the water, and a simultaneous 
contraction of the outer membraneous layer, manifesting itself 
by the delicate double contour. That this layer really does 
contract will be further demonstrated hereafter. But the dimi- 
nution of the corpuscle in length and breadth may be also due to 
an increase in its thickness, caused by the swelling and consequent 
roundness of the nucleus. In a number of cases the outlines 
appear wrinkled (Fig. 19), the cause of which may be sought in a 
momentary over-distension of the membraneous layer by the endos- 
motic current of the water, and a simultaneous expansion of the 
protoplasm preceding the contraction of this layer. Quite frequently 
the nucleus is displaced from its original seat, the centre of the 
blood-corpuscle, and is seen moving about in the interior of 
the latter. This phenomenon is readily explained. In the normal 
condition the density of the protoplasm is such as to hold the 
nucleus in the centre ; but as soon as the water enters, it becomes 
lowered by the solvent action of this fluid, and in consequence the 
nucleus is set in motion by the force of the endosmotic current. In 
a number of cases, however, the phenomenon is not confined to a 
mere displacement of the nucleus, but enters into another phase by 
the entire escape of this body through a small rupture of the mem- 
braneous layer (Figs. 21 and 22). Such an escape of the nucleus 
does not take place very rapidly, as might be thought ; but in most 
cases is a slow process, offering ample time for observation. From 
this fact we may conclude that the orifice produced by the rupture 
in the membraneous layer is at first scarcely large enough to allow 
the nucleus to drop out ; but that it is rather gradually enlarged by 
this body being pressed through it by some propelling force from 
behind. The whole phenomenon may be explained as follows : 
When the water enters into the interior of the blood-corpuscle, it 
is taken up by the protoplasm, and its first efiect is a swelling or 
