250 
unite into a small distinct corpuscle, in virtue of the law of 
localisation, all the while continuing to perform in the 
economy of the organism the same functions as when they 
were scattered in the nucleo-cellular layer. It is this same 
law which is apparent in the progressive complication of any 
cell whatever, of a muscular cell, for example, when the 
myosin, at first scattered in the protoplasm, accumulates at a 
special point of the cell, in which one can then distinguish 
a protoplasmic body, and a part formed of contractile 
substance. 
It is the same law, again, which presides over the forma- 
tion of organs by division of labour ; the biliary cells, scat- 
tered in the lower animals among the epithelial cells of the 
digestive-tube, continue to fulfil the same function when they 
have become united in such a way as to form a particular 
organ—the liver—which presides over the secretion of the 
bile. 
All around the nucleolus can soon be distinguished a per- 
fectly transparent zone, free from molecular granulations ; 
but it is not possible to determine the limits of this zone 
(figs. 18 and 21). 
The pseudo-filarium continues to shorten itself, and the 
protoplasmic filament soon becomes a body of more or less 
oval form (figs. 20 to 22), presenting often towards its middle 
a slight attenuation (sometimes the pseudo-filaria take on the 
biscuit-form, fig. 19). This body is limited by a dark con- 
tour, except at its anterior extremity, where this contour is 
much more pale. In some individuals the protoplasm bulges 
out at this point in such a way as to form either a discoid 
flattened eminence (figs. 19 and 20), or a hemispherical pro- 
tuberance (figs. 21 and following). Sometimes this is situated 
in the main axis of the body, at other times it is placed a 
little on one side (fig. 25). It is in this anterior, somewhat 
prominent part, that the refringement-granules are always 
found in greatest number. They are to be distinguished 
also, but less numerously, in all that portion of the body 
situated in front of the nucleus. But it appears that all these 
granules have a tendency to pass to the anterior extremity 
of the body, and accumulate in the terminal enlargement. 
Beneath the dark outline which demarcates the body of 
the young Gregarina is found a homogeneous and transpa- 
rent layer of protoplasm, in which not a trace of granulation 
is discernible. The medullary substance alone is finely 
granular (figs. 20 and following). 
The nucleolus is always very distinct ; it is a refringent 
corpuscle, always rather large, but with dimensions yarying 
