226 Short Papers and Notes. 
small amount of sarcode, so that the least pressure will reduce a 
dry, fresh-water sponge to powder, 
The study of the vital parts is attended with so much 
difficulty that it is only of late years that, with good instru- 
ments, a proper understanding of the subject has been attained. 
But the spicules upon which the classification is largely based 
are easily observed, and aside from their scientific value, make 
beautiful objects for the microscope. The spicules of the 
skeletons of the different species are all very similar, being 
simple needles of silica, sometimes slightly curved, more or less 
pointed, with the shaft either smooth or covered with spines. It 
is in statoblasts that we find the greatest variety of spicules. In 
general, the statoblasts may be said to be about the size of a 
mustard seed, varying in size or shape, but always approaching a 
globular form. On one side is an opening connecting with the 
soft matter of the interior. This soft matter is made up of a 
number of transparent sacs containing the germinal matter. The 
sacs are enclosed in a delicate membrane, which is again covered 
by a thicker chitinous coat. Outside of this is the wall or crust of 
the statoblast. This crust is composed of air-cells, in some 
species readily distinguished, whilst in others the highest powers 
of the microscope are required to resolve them. This structure 
causes the statoblasts to float when detached from the sponge, and 
probably in some cases serves to scatter the species. Again, the wall 
is accompanied by or charged with siliceous spicules of various 
forms. 
The statoblasts are usually to be found at the base of the ~ 
sponge, frequently attached to the object upon which it is growing, 
but sometimes scattered through the skeleton. In addition to the 
spicules of the skeleton and statoblasts, there is another kind, 
known as ‘‘dermal” spicules. These are generally more delicate 
than the skeleton spicules. Carter published his classification in 
1881, based on the form of the statoblast spicules. These 
characters are very constant; and as all the fresh-water sponges 
probably, and none of the marine, come under the group Spongillina 
(that is, bearing reproductive organs called statoblasts), this classi- 
fication, or some variation of it, seems an especially good one. 
Young sponges may be found as early as June, but mature 
specimens need only be sought late in the summer or in autumn. 
They are readily detected by their bristly surface. The colour 
and shape are generally more or less influenced by the position in 
which they grow. They may be found at the margins of rivers 
and lakes, and sometimes in deeper water. They are not un- 
frequently brought to the surface by dredging. The collections 
may be preserved in alcohol or by drying. But as the species 
can only be determined by examination with the microscope, it is 
