45 
EXTRACTS FROM THE FOREIGN PERIODICALS. 
ZOOLOGY. 
Silk-worm Nursery in France. —The Silk-worm nursery established at 
Neuilly by the King, —and placed under the direction of M. Aubert, has pro¬ 
duced the most satisfactory results. From 3,534 lbs. of Mulberry-leaves, 327 lbs. 
of good cocoons, 253 to the pound, have been obtained. This is, therefore, 185 lbs. 
of cocoons to 2,000 lbs. of leaves. In the south 80 lbs. of cocoons produced by 
2,000 lbs. of leaves, is looked upon as a very good breeding. 
Annelidce .—In addition to what has been before stated concerning this class 
of animals, we find, that Dr. Milne Edwards has further discovered that many 
of them have not red blood. Consequently, the principal character which has 
hitherto distinguished them, will become one of minor importance. 
BOTANY. . 
Differences existing between Pears and Apples. —A long and interesting 
memoir has been presented by M. Turpin to the French Academy of Sciences, on 
the difference existing between the cellular tissues of the Apple and Pear, which 
observations are extended to knots of wood, to ligneous kernels, to the calcareous 
concretions found in the mantle of the Arions, and to the ossification of animals 
in general. Those authors most tenacious concerning the establishment of these 
two vegetables as different genera, have drawn their characters from the adherence 
of the lower part of the five styles, from their villosity, the spheroid form of the 
fruit, and the stalk being set in a cavity; characters which are frequently effaced. 
M. Turpin founds his on the absence or presence of those stony concretions 
which are to be met with in the cellular tissue of the Pear. These concretions 
he attributes to the aggregations of little globules, which by degrees become 
clogged with an indigestible matter, which is confusedly deposited in molecules, 
and from which they receive their opaqueness, hardness, and colour, and to which 
he gives the name of sclerogene. This name of sclerogene M. Turpin also gives 
to all matters which are foreign to organization, which are first held in suspension, 
then deposited and become hard in the internal cells of the hollow and elementary 
organs of tissues. Of the cause of this deposit in the Pear he is perfectly ignorant 
at present, but each concretion, chemically analyzed, consists of bladders of cellular 
tissue, globules or fecula contained in these bladders, and the sclerogene, or indi¬ 
gestible matter, confusedly accumulated and mingled with the globules of fecula. 
They may be compared to numerous partial and isolated concretions in the 
