370 Mr. Hocc's Observations on the Spongilla fluviatilis, 
being deprived of light, after many days received no green tint, but continued 
of a light buff or a yellowish white colour. Thus, then, by the exactly similar 
influence of light upon the chromule*, or colouring matter in plants, and like- 
wise by the etiolation, or blanching of vegetables by the absence of light, so 
well known to every one, very favourable proofs may, from these analogous 
phenomena, be most reasonably adduced with regard to the vegetable nature 
of the Spongilla fluviatilis. 
The cireumstances that led me to the investigation of those appearances 
are described in a papert, which at the date of my former letter to you had 
not been read before the Royal Society, to whom I was induced to communi- 
cate it. I therefore did not consider myself then at liberty to make any men- 
tion of them to you; although they, together with some observations on the 
seedlike bodies of the Spongilla, already described in that letter, created in my 
mind considerable doubts as to the animality of that substance. Renewed and 
similar observations upon several fresh and living masses of the River Sponge, 
during the summer which has just passed, have now confirmed me in the cor- 
rectness of those doubts, and in the certainty of those facts which afford the 
stronger proofs of the real vegetability of that Sponge. Of such proofs, indeed, 
Which I was then about to pronounce as quite conclusive on that point, are the 
effects that I had noticed, caused by the presence and absence of light, upon 
the colours of that substance, the germination of its seedlike bodies, sporidia, or 
sporules, and their subsequent plantlike mode of growth and of increase; and 
Whilst engaged in these researches, I was greatly surprised in discovering (on 
the 12th of August, 1838,) the only traces that could with any degree of pro- 
bability be advanced in favour of the supposed animality of the Spongilla, 
namely, certain remarkable germlike bodies swimming about in the basin of 
water, wherein a beautiful mass of that Sponge, 
attached to a stone, 
D 
growing with great vigour and 
was contained. At first I was disposed to think that they 
* Prof. DeCandolle uses this term to signify that matter which produces the colours in flowers, the 
green in leaves and other parts of plants, and is contained in their cells in the shape of globules.— 
See Organographie Végétale, tom. i. p.19. Paris, 1827. 
T See a short notice of this paper in the Philosophical Magazine, 
1838; and another entitled, * De l'Action 
Bibliotheque Universelle de Gen?ve, 
vol. xiii. p. 457, for December 
de la Lumiére sur la Couleur de l'Éponge de Rivière,” in the 
tom. xix. p. 207. (Janvier, 1839). 
