FRESH WATER SPONGES OF NOVA SCOTIA—MACKAY. 235 
It is upon the distinet and invariable characters of this stato- 
blast spiculation that the modern genera are based. Some 
sponges have a third class of spicules on the surface ‘and in the 
interstitial spaces or flesh. They are always slender, and very 
much smaller than the skeletal spicules. Nearly all the sponges 
taken in Nova Scotia have been of some shade of green when 
living and exposed to the influence of light. When attached to 
the under side of stones so as to be excluded from the light, they 
become whitish. When dried rapidly, most of the sponges 
shrink considerably, yet preserve their approximate form and 
colour without decomposition. Exposure to light, however, 
soon destroys the green of the dried sponge. The great bulk of 
the specimens secured have been taken from water varying from 
a few inches to seven or eight feet. Specimens have been taken 
from between thirty aa forty feet of water by the dredge. 
They grow attached to submerged pieces of wood, bark, weeds, 
stones, gravel, and even on ferruginous concretions. Water liable 
to become turbid is unfavourable to their development. The 
largest specimen was one of Meyenia fluviatilis, taken from a 
depth of seven or eight feet, in the Garden of Eden Lake, Pictou 
County, on the Ist of August. It was encrusting a small branch 
of abont one inch in thickness, which was projecting from a 
submerged tree. It was fusiform in contour,—the greatest 
diameter being four inches, and its length twenty-seven inches. 
During winter these sponges generally die, and the most of their 
spicules are scattered in the neighboring deposits. The stato- 
blasts are also often drifted about, and germinate the following 
spring when a congenial environment is found. 
We give the following systematic outline descriptions of the. 
species collected : 
Genus I.. SPONGILLA. 
Statoblasts, more or less spherical, single or aggregated in 
larger masses about the size of a head of a pin, jared with 
linear spicules, straight or curved, cylindrical or acerate, more or 
less spined and arranged tangentially to the chitinous coat of the. 
statoblast. 
