60 CLASSIFICATION AND CREATION. 
however, a connection with his past home by a 
siphon that runs through the whole succession 
of chambers. The readers of the “ Atlantic 
Monthly ” cannot fail to remember the exquisite 
poem suggested to the Autocrat of the Break- 
fast-Table by this singular feature in the struc- 
ture of the so-called Chambered Shells. 
Cuvier divided the Mollusks also into a larger 
number of classes than are now admitted. He 
placed the Barnacles with them, on account of 
their shells; and it is only since an investigation 
of the germs born from these animals has shown 
them to be Articulates that their true position is 
understood. They give birth to little Shrimps 
that afterwards become attached to the rocks 
and then assume the shelly covering that has 
misled naturalists about them. They ought 
therefore to be referred to the class of Crus- 
tacea, in which they are now generally included. 
Brachiopods formed another of his classes; but 
these differ from the other Bivalves only in 
having a network of bloodvessels upon their 
mantle, in the place of free gills, and this is 
merely a complication of structure, not a differ- 
ence in the general mode of execution, for the 
position and relation of these organs to the rest 
of the structure are exactly the same in both. 
Pteropods constituted another class in his divis- 
ion of the type of Mollusks; but these animals, 
