REPORT ON ZOOLOGY. 189 



authors term the soft appendages of the body, that they derive 

 the characters of their four primary divisions or orders, to which 

 they attach the names of Annelides errantes, Annelkles tubicoles 

 ou sedentaires, Annelides terricoles, and Annelides suceuses. 

 Audouin and Edwards have paid particular attention to the ex- 

 ternal organization of the Annelida, and have made some inter- 

 esting discoveries with respect to the structure and use of the 

 setcB with which the feet are provided in the animals of their 

 first division, being those in which the organization is most com- 

 plex. They have observed that these setae are not mere orna- 

 ments or organs of motion, but offensive weapons of a very par- 

 ticular structure, and such as can only be compared to the stingg 

 of bees or the spines of certain fish. Savigny had noticed that 

 they were in general capable of being exserted from the body 

 and retracted at pleasure, but does not appear to have entered 

 so deeply into the details of their structure as these authors. 

 MM. Audouin and Edwards have submitted them to a close 

 and microscopic examination, and have ascertained, that while 

 some are simple, assuming a great variety of different forms, 

 others are compound, always consisting of two parts, united by 

 an articulation, which gives way when the seta is employed for 

 offensive purposes, leaving the apical portion in the body of the 

 animal attacked. 



From giving a detailed account of the external organization of 

 the Annelida in general, MM. Audouin and Edwards proceed 

 to the subordinate groups. So far as they have hitherto ad- 

 vanced in the subject, they have described at length the charac- 

 ters of all the families and genera ; but in regard to species, of 

 those only found on the coasts of France. To give any further 

 analysis of their labours would, however, be inconsistent with 

 the limits to which this Report must be restricted. It is, more- 

 over, necessary that we should proceed to notice several indi- 

 viduals who, though they have not written on this class as a 

 whole, have thrown great light upon some particular parts of it. 



The Hirudinid(B especially have received more general atten- 

 tion than any other group, which is doubtless owing to the valu- 

 able services of these animals in medicine. Dr. Rawlins Johnson 

 is the author of two memoirs in the Philosophical Transac- 

 tions for 18 17, in one of which he has detailed some interesting 

 observations with respect to the habits and mode of propagation 

 of the Hinido vulgaris ; in the other he has instituted the ge- 

 nus Glossopora * for those species in which the mouth is fur- 

 nished with a projectile tubular tongue, including the H. com- 



* The same as the genus Clepsine of Savigny. 



