£g(J ON THE CLASSES OF THE 



testinal cavity, with various other organs, and finally in 

 which the sexes seem always to be distinct. The first of 

 these groups, which is the same with M . Latreille's class of 

 Monogena, the reader will recognise as having occupied 

 the situation of a class among the Acrita, so that we have 

 only now to examine the second section. 



The Intestinaux Cavit aires of Cuvier, or Entozoa Ne- 

 matoidea of Rudolphi, are transversely striated worms in 

 which the annulose structure is more or less indistinct, 

 although perhaps never much more so, than we find it to 

 be in certain Arachnida. Now having united these " Vers 

 Rigidities " with the Epizoaria of Lamarck under the ge- 

 neral title of Vermes, I have ventured to imagine the 

 group thus constituted to be entitled to a place between 

 the Anoplura of Leach and the Chilognatha. To the 

 latter of these, or Chilognatha, they appear to be allied by 

 the cylindrical form, stiff rigid texture, and lateral spinulae, 

 instead of feet, which some of them possess. In these 

 Cylindrical Vermes the organs of respiration are not visi- 

 ble, and it is precisely among the Myriapoda that we find 

 the stigmata to become so small as in some species to be 

 imperceptible. The vestiges of Myriapod feet and the 

 cylindrical form however soon entirely disappear in the 

 Vermes; and when appendages to the body once again 

 become visible, as in the Epizoaria, it is under a quite dif- 

 ferent appearance, more analogous to that of Hexapod 

 Insects, as may be seen in the genus Entomoda of La^ 

 marck, or still better in the Cecrops of Dr. Leach. We 

 thus enter among the Anoplura, which like the Epizoaria 

 are all of a parasitical nature. 



To some of the Insects which have been just under our 

 consideration Dr. Leach has given the name of Ametabola, 



