POLYPES. 
341 
Flustra membranacea, pilosa, and Memhranipora stellata, emitted 
sparks. After he had taken these Zoophytes out of the water, together 
with the sea-weed to which they were attached, and left them dry for 
two days, the Membranipora stellata and Flustra membracea still shed 
light ; but this property was always destroyed by frost. Hassall has 
confirmed this account (ibid. viii. p. 341). 
Kolliker has published his observations on the male organs of genera- 
tion of the Flustrce (Beitr, ant. cit. p. 46). 
The appendages of the Cellularia avicularia, resembling a bird’s 
head, have been minutely examined by Nordmann (Observations sur 
la Faune Pontique, 1840, p. 679). The mass of this appendage is cal- 
careous, the bill opens and shuts, whilst the head turns from one side to 
the other ; all these motions are quite independent of the unfolding of 
the tentacula of the polype. In Bicellaria scruposa, Nordmann observed 
similar moveable bodies, the use of which he has not yet been able to 
make out. He saw the fourteen tentacula of the polypes of Cellularia, 
placed in a circle, and covered with vibratile cilia. The increase of the 
Cellularia, according to his observation, goes on in a fourfold manner, 
by stolons, gemmules, and two sorts of eggs. 
Various remarks have been made on the organization of the tufts of 
polypi in fresh-water, as well as on their development, by Coste (Compt. 
Rend. t. xii. p. 724, and Fror. Neue Notiz. Bd. 19, p. 10), and Laurent 
(I’lnstit. 1841, p, 225). We are indebted to Nordmann for a very exact 
description of the Plumatella campanulata, of which Plumatella re- 
pens, Mull., is only a variety. This sort of polype is also propagated 
by gemmules, and two sorts of eggs, namely, summer and winter 
eggs. 
Hassall has observed (Ann. Nat. Hist. x. p. 153, and Fror. Neue 
Notiz. Bd. 24, p. 90), that Plumatella repens and Alcyonidium stag- 
norum, belong to the same genus, and perhaps even to the same species, 
for the difference in the mode of branching can scarcely be regarded as 
affording a character of generic importance. Plumatella repens is only 
attached to leaves, which, after a few weeks, become decomposed, invol- 
ving the Zoophytes upon them in their own destruction ; Alcyonidium, 
on the contrary, attaches itself to stems of vegetables, and other firm 
substances, which do not decay so soon ; and allow time for some of the 
specimens to become as large as the closed hand. 
Johnston has turned his attention to the Sponges and Lithophytes 
(History of British Sponges and Lithophytes, 1842). He could not 
convince himself that these forms actually belong to the animal king- 
dom, for he found no animal irritability in the sponges, nor could he 
find polypes nor animal viscera in them. So long as the sponges are 
fresh and lively, they draw in and put out water, as he has very dis- 
tinctly observed in Halichondria papillaris, Flem. He also saw them 
385 2 B 
