288 ON THE CLASSES OF THE 



singular genus "^ycteribia points out the transition of Na- 

 ture from the Arachnida to the Insectes Suceurs of La- 

 tredlle, or Haiisteltata of Clairville, which again by some 

 of Kirby's Trkhoptera leads us to the Insectes Broi/eurs, 

 or Mandibulata of Clairville. If all these transitions be 

 natural, the real distribution of the Annulosa will be readily 

 perceived to advance in order of affinity as follows : 



Ametabola, 



Crustacea, 



Arachnida, 



Haustellata, 



Mandibulata. 

 It may however be observed, that for the present, and 

 until we shall have seen its remarkable regularity, and 

 its coincidence with those principles of minuter division 

 which I conceive to be indisputable, this arrangement 

 ought by no means to be accounted as proved. Thus it 

 may be asked. Why should the Crustacea be so far removed 

 from the vertebrated animals when they possess an organ 

 of hearing, a heart, and a branchial system of respiration, 

 of all which the Ametabola and of the two former of 

 which the Annelides are totally deficient? Now this is a 

 question that we cannot touch upon without taking some 

 notice of the scientific dispute which has of late agitated 

 the French Institute, with respect to the proper means 

 of transition from the unvertebrated to vertebrated ani- 

 mals, and without considering with that attention which 

 they really deserve the opinions which have been ad- 

 vanced on both sides of this controversy. 



M. Geoffroy de St. Hilaire, well known as one of the 

 most able professors in Europe of the Zoology of Mam- 

 malia and Birds, has in a late very singular work detailed 



