468 Analyses of Books. (Dec. 
rié came forward, and completely overpowered it. They seldonz 
attacked the worm openly, seemingly aware of the difficulty of thus 
overcoming it, but seized upon it, as it were, by stealth, gliding 
ently underneath it, and then projecting and affixing this organ, 
eeping a firm hold until they had concluded their repast. Dr. 
Johnson at first imagined the sole use of this organ to be that 
of effectually securing their prey ; but he observed that while 
they kept it firmly affixed, they moved their heads freely from 
side to side; and he found from a number of experiments, that 
when the planarie were perfect animals, they constantly received 
their food by this organ, and not by the mouth. In the event, 
however, of their being naturally or artificially divided, or of 
their losing this tube, which was not unfrequently the case, they 
took their usual sustenance by the mouth. Thus an animal fur- 
nished with a proper mouth, receives its food by another organ, 
that organ being placed as near to the tail as to the head. 
The P. lacteaand P, brunnea “ are oviparous, producing eggs, 
within a membranous capsule, each egg containing (at least those 
of the P. dactea), from three to eight young.” But these animals 
have another mode of perpetuating the species, which “ does 
not appear yet to have been noticed;” this is “ by a natural 
division of the body into two portions, the head part reproducing 
a tail, and the tail a head, in about 14 or more days, depending 
upon the state of the atmosphere.” Preparatory to this division, 
the posterior portion of the body first widens, and afterwards the 
animal has the segmented appearance of an insect. ‘“ On 
the third day, the separation of the head from the tail usually 
takes place. When undergoing this division, they remain for 
the most part stationary, keeping the head firmly affixed, twist- 
ing round the tail from time to time with a view of lessening its 
adhesion, and thus more readily effecting its disunion. Almost 
immediately after the head is liberated, it is seen to move with 
all the freedom of the unmutilated, perfect animal. The tail 
generally remains attached, and only occasionally shifts its situ- 
ation; but if touched, it moves with nearly the same quickness 
as the anterior extremity, preserving a uniform gliding motion.” 
The reproductive power of these animals when artificially 
divided is alluded to by Muller, Shaw, and others: Dr. Johnson 
describes some curious experiments on the subject. 
XXXIII. Some Experiments and Researches on the Saline Con- 
tents of Sea-water, undertaken with a View to correct and improve 
ats Chemical Analysts. By Alexander Marcet, MD. FRS. 
Honorary Professor of Chemistry at Geneva. 
XXXIV. On the Ultimate Analysis of Vegetable and Animal 
Substances. By Andrew Ure, MD. FRS. 
Dr. Marcet’s paper, which displays the elegant precision that 
distinguished all researches of its lamented author, shall be given 
in a future number of. the Annals; and of Dr. Ure’s communi- 
cation we shall take an opportunity of inserting an abstract. 
