275 
Nature of the Spongilla Friabilis. 
flame of a candle, they diminish to a third of their usual size, 
become quite black, shining, and smooth on the surface, empty 
within, and very brittle ; this was observed before the time of 
Linnaeus. In this calcined state they produce no effervescence, 
and undergo no change in the strongest acids. 
The soft matter contained within these yellow spheres, con- 
sists of two or three hundred soft transparent gelatinous globules, 
adhering slightly together, and, when magnified by the micro- 
scope, very much resembling the spawn of a frog; there is like- 
wise a small quantity of a thin colourless fluid., and some lively 
monades, as we And within the ova of most animals, but not, as 
far as I know, within the seeds of plants. When shaken gently 
in water, or allowed to remain a few minutes in it, the transpa- 
rent globules fall separate, and begin to dissolve ; on examining 
them with the microscope when thus separated, we observe that 
each globule contains about a hundred very small white opaque 
particles, which lie close together on one side of the globule, 
and occupy about a third of its capacity. The transparent part 
of the globules quickly and entirely dissolves, and the white 
opaque bodies they contained are observed strewed over the 
bottom of the water, partly adhering in groups, and partly iso- 
lated. I have not observed any change in these white particles, 
after preserving them some time in water, though they seem to 
possess the power of slowly changing their positions, when at- 
tentively watched through the microscope. 
The yellow spheres whose contents have been described, did 
not undergo the slightest perceptible change in external appear- 
ance, or in the nature of their contained matter, during six 
weeks rest in rain water, frequently renewed, from the middle 
of October to the end of November, although the true ova of 
the spongilla were growing and spreading on watch-glasses im- 
mersed in the same vessel of water. And what appears a re- 
markable circumstance, whether these bodies be ova or grains, 
their colour, size, structure, and contents, were precisely alike, 
during all the six months I have yet been able to examine the 
spongilla alive those taken from the spongilla in February 
presented the same appearances, externally and internally, as 
those of September. They differ from the ova of every marine 
sponge I have yet observed, in their strong cartilaginous cap- 
