See SR Se EA SE Tat Se any 
5 Sa aaa ee 
Geology and Natural History. 493 
which it produces has a peculiar taste and odor. The species pro- 
duces no age o.) nor can it cause an alcoholic fermentation in 
saccharose solutio The cells are ae tenacious of life, can 
be kept dried mercial months, and in this condition exposed to 
marked variations of the thermometer without i yesen anjury. 
On an Organism which puedes and ened balay Sitocons 
Spongeapicuen sepone ee aster by Professor P. 
TIN Duncan which I made to the a Rove 
Microscopical S Sotict aes on ‘Bace ri 1881, the presence of green-col- 
or 
a granular plasma of the same tint within enlargements of the axial 
canals was noticed; and the penetration and erosion were stated 
to be due to the organism. The cells which were observed within 
positions where erosion from without inwards could readily occur, 
were very small,—not more than 7000 repli in length, and very 
to er ae silica and catenis the canal in a most remarkable 
ae 
ra while the spicule suffers solution of its continuity by the 
thinning sii within, and the thinnest flakes present a granulated 
appeara 
Since erie g that communication I have observed siliceous 
sponge-spicnles, bined from great depths, which are affecte 
an organism whose cells are much larger and whose penetrations 
therefore are wider and much more visible. On the head of a large 
spinulate apical I found many circular pits, each containing an 
anic mass without definite cell-wall, and ye et granular and green 
W an 
are seen on other spicules; but, they are 203 and resemble cylin- 
rical tubes with hollowed- out bottoms. ‘Some reach the axial 
become 
zoospores of Achlya penetrans Duncan (Proc. Royal Soc,, vol xxv, 
pl. vi); the second is larger; and in both there is a decided green 
tint. No ramifications of the penetrating cylindrical tube occur; 
and it pierces perpendicularly to the surface of the spicule, or, it 
may be, slightly aslant. 
