SYSTEMATIC ARRANGEMENT. 
13 
the Crustacea, and later observations still, especially those 
of M. Nordmann, have proved them to belong decidedly 
to this class. This latter naturalist has pointed out the 
changes in form they undergo in their progress to matu- 
rity, showing them when young to be very nearly of the 
appearance of the young of the Cyclopidae, und under- 
going like them a series of moultings before they reach 
the mature state. 
Another great addition has also of late years been 
made to the class Crustacea. In consequence of the 
increased attention that has been paid by naturalists to 
the habits and formation of the molluscous animals, 
the Cirripedes w r hich formerly w T ere generally considered 
to be molluscous, from their being inclosed in a hard 
shelly case, have now been proved to be crustaceous. 
The observations of Thompson and Burmeister have de- 
monstrated them to undergo a change of form in early 
life, being, when first hatched, unattached and floating 
freely about in the sea, and not attaining their perfect 
shape till after several moultings have taken place. 
Having, in addition to these relations, jointed, ciliated 
limbs also, they approach very closely to the Entomos- 
traca. Amongst them, indeed, they have been introduced 
by Mr. J. E. Gray, in his arrangement of the Annulosa, 
in the Synopsis of the British Museum, 1842. 
The following table will give a connected view of the 
arrangement of the British Entomostraca which I propose 
to adopt. 
