ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
49 
lower of which is alone visible to the naked eye. The epithelium con- 
sists of short ciliated cylindrical cells in the grooves, while the cylin- 
drical cells of the side-walls are longer. The author concludes with a 
technical diagnosis of this interesting species. 
Antipathidse of Bay of Naples.* — Herr G. v. Koch finds five species 
in the Bay of Naples, all of which belong to the genus Antipathes, and 
exhibit in common a number of essential characters, which are briefly 
described. Very little is known of the biology of these colonies of 
polyps, owing to the difficulty of keeping them alive for any length of 
time in an aquarium ; as to the mode of growth of the colonies, more 
has been made out by comparative methods than by direct observation. 
In all the species examined by the author, there are numerous branches 
and twigs on which smaller polyps often alternate with those of normal 
size ; these smaller forms are younger. If they are followed through all 
the stages of their development it is seen that they commence as tubular 
prolongations of the larger polyps, and that they push out two, four, 
and then six tentacles ; while this is being effected the larger septa and 
the oesophageal tube are laid down, and they gradually become normal 
polyps. The species described in the present paper are A. glaherrima 
Esper, A. gracilis sp. n., A. suhpinnata Ellis, A. larix Esper, and A. 
aenea sp. n. 
Method of Defence among Mednsse-t — Mr. J. W. Fewkes draws 
attention to a method of defence among Medusae, which consists in dis- 
colouring the water by the emission of coloured pigment from certain 
chromatic cells on the bracts ; these cells are related to, and are perhaps 
homologous with, the nematocysts in other genera of the groups in which 
they exist. Their presence has been observed in only one or two genera 
of Siphonophora. The known facts appear to be : — (1) Certain Agal- 
midaB, Forskaliidas, and Apolemiidae discharge a coloured fluid from 
their cystons, or hydrocysts v^ith “ mouths.” This fluid is regarded as 
an excretion, and is supposed by Haeckel to be the means of protection, 
just like the sepia of the Cephalopoda. (2) Agalma itself has pigment- 
glands on the bracts, which discharge their contents when the covering- 
scales are broken from the stem ; this discharge probably takes place on 
simple irritation. (3) Certain Hippopodiidas and one Calycophore are 
known to change colour somewhat on irritation. (4) Nanomia has a 
prominent pigmented “ oil-globule ” at the base of the cyston, which 
has never been seen to discharge its contents. Our ignorance of the 
physiology of Jelly-fishes is so great, that we can at present hardly go 
further than this, though it is obvious that a number of interesting 
questions easily arise. 
Porifera. 
Fresh-water Sponges of Florida.^ — Mr. E. Potts gives an account 
of some fresh-water sponges which are of interest on account of the 
unusual situations and circumstances in which they were found. Most 
had grown on the stem of coarse grasses, where they formed spindle- 
* MT. Zool. Stat. Neapel, ix. (1889) pp, 187-204. 
t Ann. and Mag. Nat. Hist., iv. (1889) pp. 342-50. 
X Trans. Wagner Free Inst, of Science, ii. 3 pp. (separate copy). 
1890. E 
