SYSTEMATIC ARKANGEMENT. 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 then* progress to matu- 

 rity, showing them when young to be very nearly of the 

 appearance of the young of the Cyclopidae, and 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 which formerly were 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 eai-ly 

 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. 



