74 
NOTE ON LINGULA LESUEURL 
contains four species, viz., Lingula Lesueuri , L. Haivkei, L. ? 
Saltern, and Dinobolus Brimonti. In the “ Gres Armoricain” of 
Bagnoles, Department de l’Orne, I found Lingula Lesueuri, 
L. Hawkei, L. Salteri (very large and abundant), and Dinobolus 
Brimonti (rare). In the same rock and formation in the Depart¬ 
ment de la Sarthe are Lingula Lesueuri (small), L. crumena 
(abundant), and L. Criei, JDav. (very abundant); but in the 
Department de la Sartlie Mr. Guillier found no examples of 
Lingula Hawkei nor of Dinobolus Brimonti. At Budleigh- 
Salterton we have Lingula Lesueuri, L. Hawkei, L. crumena, 
L. Salteri, and Dinobolus Brimonti; so that the only species 
not found in our British quartzite pebbles is the Lingula Criei. 
In a very instructive paper by the Rev. P. B. Brodie 
“ On certain Quartzite and Sandstone Fossiliferous Pebbles 
in the Drift of Warwickshire,” published in the “ Quarterly 
Journal of the Geological Society” for August, 1881, will 
also be found many points of much interest relating to the 
possible source of derivation of the quartzite pebbles of the 
Midland Counties. 
Cohn’s Calculation of the Multiplication of Bacteria. —Let us 
suppose that a bacterium divides into two in the space of an hour, 
then into four at the end of a second hour, then into eight at the end 
of three hours; in twenty-four hours the number will already amount 
to more than sixteen millions and a half (16,777,220); at the end of 
two days this single bacterium will have multiplied to the incredible 
number of 281,500,000,000; at the end of three days it will have 
reached forty-seven trillions, and at the end of about a week, a 
number which can only be represented by fifty-one figures. In order 
to render these numbers more comprehensible, let us consider 
the volume which may result from the multiplication of a single 
bacterium. The individuals of the most common species of rod- 
bacteria present the form of a short cylinder having a diameter of 
a thousandth of a millimetre, and about one five-hundredth of a 
millimetre in length (that is, about 1-12,500 of an inch long by 
1-25,000 of an inch broad). Let us figure to ourselves a cubic milli¬ 
metre. This volume would contain, according to what we have just 
said, 683,000,000 bacteria, without leaving any empty space. Now, at 
the end of twenty-four hours, the bacteria coming from a single rod 
would occupy the fortieth part of a cubic millimetre; but at the end 
of the following day they would fill a space equal to 442,570 of these 
cubes, or about half a litre. Let us admit that the space occupied 
by the sea is equal to two-tliirds of the terrestrial surface, and that 
its mean depth is a mile, the capacity of the ocean will then be 
928,000,000 cubic miles. Now, the bacteria issuing from a single 
germ, the multiplication being continued on the same conditions, 
would fill the whole ocean in five days.—A. Magnin, on the Bacteria. 
