251 
in different individuals. In some there is to be observed 
in the nucleolus a small vacuole (figs. 25 and 26). 
The layer of the nucleus tends to acquire more and more 
sharply defined limits ; in all the nucleolus is surrounded by 
completely transparent zones, of a very variable thickness, 
and more or less sharply delineated (figs. 20, 22, and follow- 
ing). In small Gregarine, of the same size, very notable 
differences are to be observed in this respect. By the side of 
small Gregarinz, whose nucleolus is surrounded by a trans- 
parent thin layer sharply circumscribed, others of the same 
size are found, where the nuclear layer is, on the contrary, 
thick, but with very vague outline. The position of the 
nucleus is not more constant than its dimensions. Some- 
times it is situated in the middle of the body, and in its 
narrowest part ((fig. 19); at other times it is situated in front, 
in the broadest part of the cell; more rarely it is situated in 
its posterior half. 
We have henceforward under our eyes a young, well- 
characterised Gregarina, which has only to grow in size to 
become that fine ceil of sixteen millimétres in length, which 
well justifies the name of Gregarina gigantea, which I have 
given to it. 
The body elongates progressively, assuming more and 
more clearly the shape and the characters of a cylindroid sac, 
a little enlarged only in its anterior fourth. But the poste- 
rior part of the body elongates more rapidly than that which 
is situated in front of the nucleus, and from this it follows 
that the latter, which in all the young Gregarine occupied 
generally the middle of the body, exhibits itself now con- 
stantly at the line of junction of the anterior third of the 
body, with the two posterior thirds, as in the adult (fig. 26 
and following). 
The little enlargement of the anterior extremity of the 
body, which is often hemispherical, has also developed itself ; 
only it is no longer circumscribed by a so clearly marked 
form. It is continuous almost insensibly with the rest of the 
body, from which it is no longer separated, except by aslight 
constriction (26 and 27). 
The refringent granules which have accumulated in this 
terminal enlargement have agglutinated themselves into a 
mass separated from the granular protoplasm of the axis of 
the sac by a perfectly transparent layer of protoplasm. This 
layer forms, in the interior of the sac, a transverse partition, 
which divides the cavity of the sac into two chambers—the 
one, anterior, very small, is filled with refringent granules, 
which were at first scattered in the anterior portion of the 
