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in the form of canals into the velum, a peculiarity which he thinks will neces- 
sitate the formation of a new family or sub-order for this animal. 
The little freshwater Medusa from the Victoria tank, has been described 
by Prof. Allman and Prof. Lankester, and has the questionable privilege of 
already possessing three names. Prof. Allman named it Limnocodium 
Victoria , in a paper read before the Linnean Society ; Prof. Lankester in 
Nature gave it the denomination of Craspedacusta S owerbii, but changed the 
generic name to Periplanella, in a communication read to the Royal Society. 
Nothing is known as to the means of its introduction into the tank in which 
it was found: this has been used for years for the cultivation of the Vic- 
toria Water-Lily, which is an annual grown from seed ; the seed used is 
ripened in this country; and the tank is empty and dry for several months 
every year. Of course nothing is known of its life-history, except that it 
was observed by Mr. Sowerby feeding on Paphnice. Prof. Lankester regards 
it as belonging to Hackel’s order Trachomedusse, and family Petasidse, 
and as probably most nearly allied to the genus Aglauropsis of Fritz Muller, 
from the coast of Brazil. It is therefore probably one of those forms of 
Medusae which have no fixed polyp-like stage in their development. 
Prosopistoma. — M. Vayssiere has continued his studies upon this curious 
insect (see Pop. Sc. Rev., N. S., vol. ii. p. 444) which was supposed to be a 
permanent aquatic form of the Ephemeridae. He has now observed its 
metamorphosis, and describes the results as follows : — Towards the end of 
May, the amber-yellow colour of some of the specimens which he was 
keeping in captivity became less bright, and he could soon see through the 
skin the first lineaments of the new individual. A few days afterwards 
(on the 3rd of June) the animals escaped from the pupal envelope in the 
same way as the ordinary Ephemeridae. In the perfect state Prosopistoma 
closely resembles the well-known genus Coenis, so that its right to enter into 
the Ephemerine family is established. Its last segment bears three rudi- 
mentary bristles, representing the natatory setae which it possesses in its 
aquatic form. ( Compt . Rend., 7th June, 1880.) 
