192 
POPULAR SCIENCE REVIEW. 
A New Standard of Light has been suggested by Mr. Louis Schwendler, 
in the Journal of the Society of Bengal. It consists of a U-shaped piece of 
platinum foil, about 20 mm. in length, each limb being 3 mm. in breadth, 
and at the top with metal clips : a current, the amount of which is registered 
by a galvanometer in circuit, is passed through this. It is a step in advance 
of the candle standard, though not of the same accuracy as other scientific 
units. 
Coloured Rings on the Surface of Mercury have been obtained by M. 
Guebhard, by clearing it of oxide and breathing on it. They contract as 
evaporation diminishes the thickness. The best results are obtained with 
collodion, diluted by means of ether. These pellicles can be detached and 
transferred to paper. 
ZOOLOGY. 
A Synthetic Starfish. — Under the name of Astrophiura permira, Mr. W. 
Percy Sladen has described (. Annals and Mag. Nat. Hist. December, 1879) 
a most remarkable form of Echinoderm from the coast of Madagascar. While 
the ordinary starfishes present usually the well-known star-like form, with 
five or more rays springing from a central body with which they are perfectly 
continuous, the body in the Ophiurids is a rounded or more or less pentagonal 
disc, from which issue five jointed arms, quite distinct in structure from the disc 
and from the much stouter rays of the ordinary starfishes. Mr. Sladen’s new 
form combines the characters of the two groups in a very singular manner ; 
and curiously enough, it is towards the somewhat aberrant forms of starfishes 
(such as Goniodiscus ) in which the enlargement of the disc and shortening of 
the rays converts the whole body into a pentagonal disc, that the new type 
seems most to approximate in outward appearance. In fact, the arms are 
for the greater part of their length enclosed in a disc formed of calcareous 
plates both above and below, but a small portion of jointed arm projects from 
each angle of the pentagon thus formed, and with the stiucture displayed 
along the lines of the arms on the lower surface sufficiently demonstrates the 
Ophiuridan affinities of the organism. By careful study indeed Mr. Sladen 
makes out that the whole skeletal structure is due to an abnormal develop- 
ment of the ordinary plates of an Ophiurid ; but at the same time he 
recognizes in the structure of the animal a number of characters which tend 
towards the Asteroida, such as a great development of the ambulacral system, 
with formation of supplementary plates separating the tentacular compart- 
ments, the extension of the peritoneal cavity into the radial portions of the 
anima 1 , and the organization of the mouth. Mr. Sladen’s paper, which is 
illustrated with an excellent plate, deserves the attention of all zoologists. 
l /rt/vv — Q-j'i 
CXj^ri\L/ / $ 8 / 
