OF THE ANNULOSA. 343 



have another duty still to fulfill, namely, to assign that 

 merit to others which is their due. Now, the Linnsean 

 group of Aptera is the same heterogeneous and confused 

 mass that it was in the earliest periods of Natural History, 

 although not merely the science of Entomology, but that of 

 Zoology in general, may be said in some measure to de- 

 pend on the proper arrangement of Aristotle's Apterous 

 insects. Happy would it have been for the learned Swede 

 if in this department also he had thought proper to fol- 

 low the track of Ray. 



The removal of the chief difficulties attending the inves- 

 tigation of Aptera may be dated from the moment when 

 it was observed that a number of animals, of altogether 

 difFerentexternal appearances, nevertheless agree in the pos- 

 session of two nervous strings originating in a very small 

 brain placed on the oesophagus, which these strings sur- 

 round. And when it was further discovered that these two 

 strings, proceeding along the whole length of the subject, are 

 sometimes united at different distances by double knots or 

 ganglions, Avhich disperse the nerves to the limbs and other 

 parts of the body, the externally articulated animal may 

 be said to have been insulated from all others. This ner- 

 vous system, though it may vary in its details, and parti- 

 cularly in its number of longitudinal ganglions, is singu- 

 larly conspicuous in the Cirripeda, Annulosa, and Anne- 

 lides. But as the former of these three groups consists of 

 hermaphrodites, destitute of the facultyof locomotion, with 

 a body not strictly articulated, and as the Annelides are 

 hermaphrodite red-blooded animals, the Annulosa are not 

 likely to be confounded with either. We have elsewhere 

 seen that the Annulosa may be characterized as white- 

 blooded animals having the nervous system above de- 



