ergy. A mixture of chlorine and hydrogen gases diluted with 
ir or oxygen combines slowly in light. Without air the mix- 
re is exploded (as Tyndall has shown in well-known experi- 
ents) by exposure to white light, the chemical rays being most 
cient. M. Dufour has examined the behaviour of this mixture 
S to its power of yielding radiophonic and photophonic sounds 
hen illuminated by intermittent beams of different kinds, as in 
he researches of Graham Bell and Tainter. He finds that the 
loudest sounds occur when violet and ultra-violet rays are em- 
loyed, no sound whatever being produced by red rays. 
WE notice in the last number of the Fowrnal of the Russian 
Chemical and Physical Society (vol. xiii.), a paper, by M. 
Kraevitch, on the limit of rarefaction which might be obtained by 
means of mercury-pumps. M. Kraevitch affirms that in such a 
pump the tube will always remain filled with vapours of mercury, 
he elasticity of which, at ordinary temperatures, is no less than 
0’02 millimetre ; the use of desiccative substances cannot make 
these vapours disappear, as new vapours are immediately formed 
again. He contests therefore the idea that Mr. Crookes might 
have obtained in his experiments so low a pressure as 000004 
etre ; and observes that M’Leod’s gauge can measure the elas- 
icity of a permanent gas (admitting that the law of Mariotte 
rere true at such low pressures), but that it does not give the 
elasticity of the vapours of mercury. After a sketch of different 
air-pumps, he recommends that of Prof. Mendeleeff, with some 
modifications of his own, the most important of which is intended 
to eliminate the inconvenience which Mendeleeff’s pump has in 
common with that of Sprengel, namely, the adhesion of an air- 
film to the glass-tube at low pressures. ‘The rarefaction of the 
air, he says, can be carried in this pump so far as to reduce the 
elasticity of the permanent gas to o'0002 millimetre, the pressure 
of the vapours of mercury always remaining, however, no less 
than 0’02 millimetre at the usual temperature of our rooms. In 
a few hours the rarefaction may be produced as to show the 
fluorescence of glass at the negative pole and the other pheno- 
mena described by Mr. Crookes, and even to stop the transmission 
of electricity. 
THE PRIZES OF THE PARIS ACADEMY 
“THE following is, in brief, a list of the prizes offered in 
, connection with specified subjects in 1882 and follow- 
ing years:—In 1882: Grand prize of the Mathematical 
Sciences (medal worth 3000 fr.): Theory of the decompo- 
Sition of whole numbers in a sum of five squares. Extraordinary 
prize of 6000 fr. : Progress increasing the efficiency of the naval 
forces. Plumey prize (medal, 2500 fr.): Improvement of 
steam-engines, or of steam-navigation otherwise. Damoiseau 
prize (medal, 10,000 fr.): Revision of the theory of Jupiter’s 
Satellites. Grand prize of the Mathematical Sciences (medal, 
3000 fr.) : Experimental and theoretical study of the elasticity 
‘ef one or several crystalline substances. Bordin prize (medal, 
3000 fr.) : Origin of atmospheric electricity and cause of phenv- 
mena in thunderclouds. Desmaziéres prize (medal, 1600 fr.) : 
Best work in cryptogamy. Vaillant prize (medal, 4000 fr.) : 
Tnoculation as a prophylactic in contagious diseases of domestic 
nmimals. Grand prize of the Physical Sciences (medal, 3000 fr.) : 
Distribution of marine animals on the French coast. Du Gama 
Machado prize (medal, 1200 fr.) : On coloured parts of the 
tegumentary system of aniwals, or on the fecundating matter of 
animated beings. Breant prize (interest on 100,000 fr.) ; Cure 
of Asiatic cholera. Godard jrize. (medal, 1000 fr.) : Anatomy, 
physiology, and pathology of the genito-urinary organs. Lalle- 
mand prize (1800 fr.): Work on the nervous system. Gay 
‘prize (2500 fr.): Marine lacustrine and terrestrial deposits 
on the French coasts in the present period, and espe- 
cially since the Roman epoch. In addition, there are the 
Montyon prize in Mechanics, the Lalande and Valz prizes in 
Astronomy, and several others. Then in 1883: Fourneyron 
prize (500 fr.): Different modes of transmission of force to 
a distance. Grand prize of the physical sciences (medal, 
3000 fr.): Geological description of a region of France or 
Algeria. De la Fons Melicoque prize (300 fr.) ; Botanical work 
on the North of France. Burdin prize (3000 fr.) : Influence of 
medium on the structure of vegetating organs; variations of 
terrestrial plants grown in water, and of aquatic [plants in air ; 
explain by direct experiments the special forms of some species 
of maritime flora, Bordin prize (medal, 3000 fr.) : Paleeontology 
of France or Algeria. 
(medal, 3000 fr.) : Histological development of insects during 
NATURE 
Grand prize of the physical sciences | 
377 
their metamorphoses. Alphonse Penaud prize (3000 fr.) : Aérial 
locomotion. In 1884: Sener prize (7500 fr.): On genera 
embryology applied as much as possible to physiology and medi- 
cine. In 1885: Dusgate prize (2500 fr.): Diagnostic signs of 
death and means of preventing precipitate inhumation. In 
1886 the Jean Renaud prize will be awarded for the most 
meritorious work during five years. 
SYMBIOSIS OF ALG AND ANIMALS 
CORRESPONDENT sends us the following as an epitome 
of K. Brandt’s experiments on the green bodies found in 
the bodies of Hydra, Spongilla, Stentor, &c. :— 
When the green bodies are removed from these organisms by 
crushing, they are found not to be entirely and uniformly green 
like the chlorophyll-bodies of plants ; in addition to the green 
substance they consist also of colourless protoplasm. Treatment 
with hematoxylin always reveals a definite cell-nucleus ; and the 
same is the case if first killed by 02 per cent. chromic acid or 
I per cent. superosmic acid, then freed from chlorophyll by 
alcohol, and finally treated with solution of hematoxylin. These 
green bodies do not therefore correspond to the chlorophyll- 
bodies of alge, but are themselves independent organisms, 
unicellular algze. To those found in the animals named above 
the author gives the generic name Zooch/orella, to those which 
occur in the Radiolaria, Actinie, &c., the name Zooxanthella. 
Experiment proved that they are capable of carrying on an inde- 
pendent existence after removal from the animal in which they 
are found, and are able to produce starch-grains. They can 
also enter into the bodies of other animals which feed on those 
that contain them. The physiological function of these 
algze was investigated in the case of those which form the 
well-known ‘‘ yellow cells” of the Radiolaria. These were 
found to be of service in supplying food to the host, which 
thrives best in perfectly pure filtered water. So long 
as the animals contain few or no green or yellow alge, 
they are nourished, like true animals, by the absorption of 
solid organic substances ; but as soon as they conrain a sufficient 
quantity of these alge, they are nourished, like true plants, by 
assimilation of inorganic substances. In the latter case the algz 
which live in the animals perform altogether the function of the 
chlorophyll-bodies of plants. Finally the author compares the 
mode of life of these Phytozoa (as he terms the animals which 
subsist on the algz contained within them) with that of Lichens. 
With the Phytozoa there is, however, this remarkable peculiarity, 
that morphologically it is the alga, physiologically the animal 
which is the parasite. 
NOTES ABOUT SNAKES 
A SERPENT’S first instinctive impulse of self-preservation, 
like that of every other animal, lies in escape ; probably a 
more nervous creature does not exist. If surprised suddenly, or 
brought to bay at close quarters, it may be too terror-stricken to 
attempt flight; then it éz¢es, following a curious general rule 
which seems to obtain throughout nearly the whole animal world, 
from a passionate child downward, no matter what the natural 
weapons of offence may be. Young /¢/:de@ will keep their talons 
sheathed until they have exerted all possible force with their soft 
milk-teeth, and a lizard will seize the hand which restrains it 
with its insignificant little jaws, when its tail or claws might 
inflict far more injury. The Borde never use their constrictive 
powers in self-defence (unless they are gripped), and it seems 
probable that if a venomous snake’s fangs lay in its tail, it would 
use its teeth frst when attacked before bringing them into play. 
Indeed it must be remembered that very few animals are pro- 
vided with exclusively defensive weapons, and that the python’s 
enormous strength in constriction, the viper’s poison apparatus, 
the lion’s teeth and claws, and the electric discharge of the 
gymnotus are given them primarily for the purpose of securing 
their food. : 
A snake runs away, walking along on the points of its 
numerous ribs with a rapidity which can only be appreciated by 
those who have seen a long one—/erfetodryas, for instance— 
escaping in the open or over the bushes when alarmed, its speed 
being further increased by the body being drawn up at intervals 
into folds, which, being extended, shoot the head forward. This 
is the swiftest mode of. progression of which a snake is capable, 
and is, as I have said, difficult to be realised from the spectacle 
of these reptiles in cages; the Brazilian neck-marked snake 
(Geopytas collaris), at the Zoological Gardens, will perhaps con- 
