SCIENTIFIC SUMMARY. 
335- 
be made to circulate. A steam-engine of 40-liorse power consumes hourly 
80 kilos, of coal : consequently 1 kilo, of coal would give 5 kilos, of ice — a 
very favourable result. Such a machine, including the engine, cost in 1873 ; 
66,000 marks (3,300/.) The sum certainly seems immense. 
ZOOLOGY AND COMPARATIVE ANATOMY. 
The 11 Challenger ” Expedition, — Since our last issue this expedition has 
come to a conclusion. Much of the work, however, remains to be published,, 
and will occupy the different members of the staff for the next six or nine 
months. All that has been published concerning her trip around the world 
will be found in the long and important paper which was published in am 
earlier number by W. F. Galton, F.R.C.S. 
Snakes that Eat Snakes . — One of these creatures, which is now at the 
gardens of the Zoological Society, has, during its stay in this climate,, 
devoured an enormous number of the common English snake. We learn 
from an American contemporary that some years ago Professor Cope 
described the snake-eating habits of the Oxyrrhopus plumbeus (Wied), a 
rather large species of snake which is abundant in. the intertropical parts- 
of America. A specimen of it from Martinique was observed to have 
swallowed the greater part of a lar gefer-de-lance. the largest venomous’snake 
in the West Indies. The Oxyrrhopus had seized the fer-de-lance by the 
snout, thus preventing it from inflicting fatal wounds, and had swallowed a 
greater part of its length, when caught and preserved by the collector. 
More recently a specimen was brought by Mr. Gabb from Costa Rica, 
almost five feet in length, which had swallowed nearly three feet of a large 
harmless snake ( Herpetrodryas carinatus ) about six feet in length. The 
head was partially digested, while three feet projected from the mouth of' 
the Oxyrrhopus in a sound condition. The Oxyrrhopus is entirely harmless, 
although spirited and pugnacious in its manners. Professor Cope suggests 
that its introduction into regions infested with venomous snakes, like the 
island of Martinique, would be followed by beneficial results. The East 
Indian snake-eater, Naja elaps, is unavailable for this purpose, as it is itself 
one of the most dangerous of venomous snakes. 
Singular Custom adopted by a Tree-Frog . — Professor Peters has lately 
described the mode of deposit of its eggs employed by a species of tree-frog 
( ' Poly pedates ) from tropical Western Africa. This species deposits its eggs, as 
is usual among batrachians, in a mass of albuminous jelly ; but instead of 
placing this in the water, it attaches it to the leaves of trees which border 
the shore and overhang a water-hole or pond. Here the albumen speedily 
dries, forming a horny or glazed coating of the leaf, inclosing the unimpreg- 
nated eggs in a strong envelope. Upon the advent of the rainy season, tho 
albumen is softened, and with the eggs is washed into the pool below, now 
filled with water. Here the male frog finds the masses, and occupies him- 
self with their impregnation. 
Crustacea of the North Eacijic Exploring Expedition. — It was supposed that 
the papers of Dr. Stimpson describing these Crustacea had been destroyed. 
