STRUCTURE OF THE LANCELOT. 51 



ranged in the class of fishes, and yet have neither 

 gills nor branchial arches, is as wide a departure 

 from the common analogies of nature as any of 

 those to which we have already alluded. The 

 question then here occurs, In what does the respi- 

 ratory system of this animal consist ? We answer, 

 in a Hyoid apparatus which supports the mouth, 

 and in a range of what may be called tracheal 

 rings, — corresponding to the windpipe, — which 

 supplies the place of gills. The hyoid apparatus 

 guards the entrance of the mouth in form of a 

 longitudinal slit, and is divided into many mi- 

 nute pieces. Immediately behind this apparatus, 

 what may be called the tracheal cavity commences, 

 and continues as a dilated tube till it at length con- 

 tracts, and becomes continuous with the cligestive 

 portion of the intestine. The walls of the two an- 

 terior thirds of the tracheal cavity are strengthened, 

 on each side, by a series of transparent rings to the 

 number of seventy or eighty, hair-like and highly 

 elastic, which are imbedded in their substance, 

 their general direction being from above doAvn- 

 wards. There results from this arrangement a sort 

 of skeleton canal, the walls of which are completed 

 by membrane ; and thus is formed an apparatus for 

 respiration which has hitherto been unobserved in 

 the class of fishes. This fish then respires, by re- 

 ceiving sea-water into the anterior compartments 

 of its intestinal tube, thus kept dilated by these 

 filamentous rings: and the dilatation may be in- 

 creased by the action of the superimposed lateral 



