80 
REPORT ON BOTANY, MDCCCXLI : 
has been represented very much enlarged, breaks forth and 
forms the soredium. The external cellular integument, which 
is seen very much enlarged in fig. 13, on the other hand, is 
broken through, and nothing of it goes to the soredium. I 
doubt very much if the individual propagation of Lichenes 
takes place by soredia. 
ALG^. 
Remarks on Spongilla fluviatilis, by John Hogg, in Tran- 
sactions of the Linnaean Society of London, vol. xviii. part iii, 
(1840), p. 363 and 368. The author, in his first essay, declares 
himself in favour of the vegetable nature of this organization. 
He says, that he cannot believe that the seed-like bodies of the 
Spongilla are the eggs of a Cristatella (pagans'), since he has 
never found such a Cristatella in their vicinity. In the 
second essay he relates, circumstantially, his observations on 
the Spongilla. In the year 1838, he observed some germ-like 
bodies, which floated about in the vessel in which were a 
number of vegetating Spongillm. They were small, but visible 
to the naked eye, of a globular, or rather of an oval shape ; 
the lower and smaller part is opaque, the upper transparent 
and membranous. Their movements were as remarkable as 
they were elegant ; they rose from the Spongilla at the bottom 
of the vessel to the surface, and either floated slowly on the 
surface, or roamed through the water like a balloon in the air. 
They approached or removed themselves from each other; 
calmly suspended themselves in a given spot, or turned round 
in circles. They always, however, moved in such a manner, 
that the round part was before. He placed one of these bodies 
in a watch-glass, and renewed the water daily twice or thrice. 
At first, the body moved itself, then it turned slowly round on 
its axis ; finally, it established itself firmly, and became con- 
verted into a white opaque substance, which, as it grew in the 
water, appeared to be gelatinous, but when dry, exhibited 
small cells, and fibres, and points. About the same time, he 
made an experiment with the seed-like bodies which he terms 
sporules. He took them off from the Spongilla, and placed 
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