130 
Notes. 
alga gains in probability by the observations of Dr. Marchesetti on a 
florid ean alga ( Marchesettia spongioides, Hauck). The alga is de- 
scribed and figured by Dr. Hauck in the Atti del Museo Civico di 
Storia Naturale di Trieste, vol. vii, p. 236, Tab. 3, and Dr. Marchesetti’s 
paper, Sur un nuovo caso di Simbiosi, is at p. 239 of the same volume. 
The alga in this case is, as has been said, floridean ( Areschougiaceae ), 
is sponge-like in appearance, and is furnished with ‘ oscula.’ Small 
masses of protoplasm occupy the interstices between the tissues of the 
alga and contain many spicules, among which there are often fibuli- 
form bodies like those figured by Schmidt for Reniera fibulata (Die 
Spongien d. Adriat. Meeres, p. 73, t. 7, f. 9). On the surface of the 
alga are found spicules which form a reticulum, and completely cover 
it with a pellucid pellicle. Schulze, who determined the sponge, was 
struck by the remarkable resemblance of the alga to Chalina and 
regarded it as a case of mimicry. Dr. Askenasy has recently published 
some interesting observations on Marchesettia with an illustration 
(Forschungsreise der ‘Gazelle/ Theil IV. Botanik ; Algen, Tab. xii). 
We have very little doubt that these cases (Dr. Marchesetti’s and 
our own) are of much the same nature as those recorded by Dr. 
Carter (Ann. and Mag. Nat. Hist. 1878, p. 163) whatever their true 
explanation may be. Dr. Carter’s opinion, which is of the highest 
value, is that in the cases he records the seaweed gradually replaces 
and becomes what a mineralogist would term a pseudomorph of 
the sponge. He observed, for example, Thamnoclonium flabelliforme , 
which had replaced Reniera fibulata , and an unnamed alga, which had 
similarly treated Halichondria plumosa. 
It should have been said that Marchesettia was collected at Singa- 
pore, and that it occurs also at Nosibb, Madagascar (Hildebrandt), and 
in New-Caledonia, the locality of Spongocladia neocaledonica, Grun. It 
is obvious that living material illustrating one or other of these cases 
need not be hard to find, and it may be hoped that the observations 
which alone can settle the matter will be made before long. 
Professor Bayley Balfour has kindly called our attention to the case 
of Spongia cartilaginea, Esp., especially mentioned by Semper in his 
* Animal Life/ (Internat. Sci. Ser.), p. 343. It is obviously of the 
same nature as Marchesettia , though the alga is a different one. 
Esper, in describing this remarkable association of sponge and 
alga (Pflanzenthiere ; Fortsetzung, II. p. 23, Tab. LXIII), says that 
the alga agrees with ‘ Fucus corneus or cartilagineus ’ = Gelidium 
