and the Grey Mutlet of the J^ntish Coast, iSS 



according to the figure, of four slender rays, which are distant 

 and entirely unconnected (see fig. 23, pi. 43, torn. v. of the 

 Anat. Comp.). In this, as well as fig. 24, and perhaps 19 

 (the herring), it is probable that a mistake has been made by 

 carrying the gut, or duodenum, down over the fore-part of the 

 stomach, instead of the back way, or next the spine : if it be 

 not a mistake in the drawing, then it shows a still more extra- 

 ordinary disparity with our species, the grey mullet. 



The air-bladder of the mullet is of the fixed kind, or a mem- 

 brane stretched across from side to side, covered with a pro- 

 duction, as it were, of the dark-coloured peritoneum — attached 

 along the opposite sides of the spine, and extending the whole 

 length of its abdominal cavity. This cavity, it appears, is 

 inflated with hydrogen gas ; at least I find it takes fire by per- 

 forating it and presenting a lighted taper. I have observed the 

 same in the swim-bladder of the electrical eel * (gymnotus 



* The air-bladder in this fish is large and perspicuous, although said by Bloch 

 to be destitute of this viscus. I may also notice here that many errors of this kind 

 are fallen into by Linnaeus, and former writers, even by the most distinguished 

 naturahsts of the present age. MM. Blumenbach and Cuvier observe, that the 

 common mackerel (Scomber scombrus) is destitute of the swim-bladder : and they 

 assert the same of all the pleuronectes, and several others. In these, however, I 

 find the swim or air-bladder ; that of the mackerel is precisely of the same kind, 

 although smaller, as in the mullets — ». e., a fixed bladder, as it were a duplicature 

 of the peritoneum, and similar to what we observe in the gadus, or cod kind. 



But what is rather singular, this fish (the mackerel), in which the greatest natur- 

 alists deny the existence of such an organ, contains, in fact, not one merely, but 

 two air-bladders, running one above the other immediately under the spine ; they 

 are nearly cylindric when blown up, for they are commonly found empty ; having 

 the usual attachments — i. e., on each side tlie spine — to the ovaria, or, in males, to 

 the milt, to the gills, and anterior dorsal vertebrae ; they seem to be distinct, or 

 without communication, as appears by inflating each cavity alternately with a 

 quill or small tube. I had previously observed the same structure in a sparus, sent 

 me by Mr.Hempson, No. 304, Oxford Street, in May, 1829, who called it a silver 

 starling. It appears to be a variety of S. pagrus, or a near species ; not yellow, 

 as in Uie gilt-head, but the whole body silvery. The same, also, was observed in 

 a species of clupea which was sent to me for a shad. 



TTie remora, or sucking-fish (echeneis), the mullus, the cottus, and calyony- 

 mus genera, &c., are said to want this organ. Several of these, it is true, I have 

 either neglected, or had no opportunity to examine ; having, however, found the 

 air-bladder in most of those fishes in which authors deny its existence — in all those, 

 at least, which I have examined : I am incUned even to doubt whether any true 

 fishes exist which are not provided with some hydro-pneumatic apparatus of this 

 kind ; in its form and structure exceedingly diversified in different fishes. I even 

 find it in the lamprey, a fish presenting one of the most simple species of internal 

 organization. It consists, in this fish, of a slender tube, nearly the diameter of a 

 goose-quill, rumiing along under the spine, and having the same attachments as in 

 the mullet, the cod kind, &c. : in all, it occupies the part next the spine. Here 

 Creative wisdom appears in a dear light : the buoyant power thus preserving a 



