108 
POPULAK SCIENCE REVIEW. 
the reverse of the false current, and of the currents in muscles and nerves. 
This is the true plant current, the expression of the real electricity of plants. 
Dr. Ranke styles it the strong current, using in this and in other cases a 
terminology corresponding to that of Du Bois Reymond. By a further 
cutting of the piece, either perpendicular or parallel to the axis, the current 
at first sometimes increases, but it gradually becomes 'sveaker as the process 
is continued. — See also Chemical Nexus, Nov. 29, 1872. 
ZOOLOGY. 
A xjoung Hippopotamus horn in London . — On November 5, 1872, at seven 
A.M., the female hippopotamus gave birth to a young one, which, in honour 
of the day, has been called “ Guy Fawkes.” Guy has since got on very 
well, owing to the great care which has been taken of him. In fact it 
reflects great credit on both Dr. Sclater and Mr. Bartlett; and we trust 
that the fellows will show the secretary and his sub.” that they feel so. 
The Animals of the Mammoth Cave, America. — Some time since we gave an 
account of Dr. Packard’s researches in this remarkable cavern. We now beg 
to lay before our readers some further remarks, which were made by Professor 
Silliman some time ago, and which are quoted in the “ American Natu- 
ralist,” September, 1872. Of the fish there are two species, one of which 
has been described by Dr. Wyman, in the American Journal of Science,” 
and which is entirely eyeless ; some ten or twelve specimens of the species 
were obtained. The second species of fish is not colourless like the first, 
and it has external eyes, which however are found to be quite blind. The 
craw-fish or small Crustacea inhabiting the rivers with the fish are also 
eyeless and uncoloured ; but the larger-eyed and coloured craw-fish, which 
are abundant without the cave, are also common at some seasons in the 
subterranean rivers, and so also it is said the fish of Green river are to be 
found in times of flood in the rivers of the cave. Among the collections 
are some of the larger-eyed craw-fish which were caught in the cave. 
The only mammal, except the bats, observed in the cave, is a rat which is 
very abundant, judging from the tracks which they make; but so shy and 
secluded in their habits that they are seldom seen. We caught two of 
them, and fortunately male and female. The chief points of difierence 
from the common rat in external characters are in the colour, which is 
blueish, the feet and belly and throat white, the coat which is of soft fur, 
and the tail also thinly furred ; while the common or Norway rat is grey or 
brown, and covered with rough hair. The cave-rat is possessed of dark 
black eyes, of the size of a rabbit’s eye, and entirely without iris ; the 
feelers also are uncommonly long. We have satisfied ourselves that he is 
entirely blind when first caught, although his eyes are so large and lustrous. 
By keeping them, however, in captivity and diffuse light, they gradually 
appeared to attain some power of vision. They feed on apples and bread, 
but will not at present touch animal food. There is no evidence that the 
cave-rats ever visit the upper air, and there was no one who could tell me 
whether they were or were not found there by the persons who first entered 
