67 
Vegetative Mycelium of Saprolegnia . 
nuclear membrane. This central mass consists mostly of chromatin, and 
appears at first to be a nucleolar body. It is comparable with a similar 
body found in the vegetative nuclei of Penicillium, to which Gueguen ( 1899 ) 
applied the indefinite term ‘ chromoblast ’, as the function of this body is not 
yet realized. Its shape is usually spherical or ovoid, but in a few cases it is 
slightly flattened to a disc-like form. In some lightly stained preparations 
it appears to be fluid within, with a more deeply stained outer coat. 
In examining a long hypha of the fungus, it was noticed that the nuclei 
are neither uniform in shape nor size, but that there is a gradual transition 
in shape from a spherical form in the zoosporangium to a long torpedo-like 
form in the lower parts of the thallus. 
In the zoospore the cytoplasm is dense and fairly evenly distributed, 
Fig. 4. *A typical resting nucleus, 
spherical in shape, with pronounced 
linin threads and granules on the mem¬ 
brane. x 3,000. 
Fig. 3. The base of a hypha, where the cytoplasm Fig. 5. An elongated form showing 
is much less dense. The nuclei are long and pointed chromatin on the membrane, x 3,000. 
at the ends. x 500 and x 1,500. d.n., dividing 
nucleus; c., cellulin body. 
and the nucleus spherical, the central body of which constitutes the main 
portion. The hyaloplasm is not so broad as fn the other parts and less 
chromatin is present on the outer membrane. The size is about 3*5 jx in this 
condition, which is considered to be the resting condition. A similar state 
of affairs is found immediately below the septum, where the cytoplasm is also 
quite dense; in these nuclei the hyaloplasmic layer is slightly deeper (Fig. 1). 
A short distance below this region the cytoplasm becomes less dense, and 
there is a rapid transition from the homogeneous condition just described to 
a state in which strands appear in the cytoplasm. These at first are quite 
close together, consisting of dense cytoplasm with nuclei distributed within 
them. Between the main strands, which, because of the rapid streaming, run 
chiefly longitudinally and diagonally, is a network of finer strands. The 
latter form connexions between the neighbouring main strands, and some 
cross the lumen and connect the cytoplasm on opposite sides of the hypha. 
The quantity of cytoplasm gradually becomes less in the lower parts, so that 
