6458 Fishes. 



through its nostrils is supported by another assertion, that the 

 creature has " two well-developed cellular lungs of nearly equal size. 

 (See Owen, Trans. Linn. Soc. vol. xviii. plate 25, fig. 3, plate 26, 

 figs. 1, 2.)" 



Nothing can be more candid than the way in which Dr. Gray here 

 gives chapter and verse for the assertion he has made, and no 

 authority can be higher than that which he quotes. All that can be 

 required of a naturalist is thus to refer to the source of his informa- 

 tion, and, making the required reference, we find Professor Owen 

 using the following words : — " The lungs, for I know not how other- 

 wise to designate, according either to their physiological or morpho- 

 logical relations, those organs, which in the technical language of the 

 ichthyologist, would be termed the swim- or air-bladder." Here then 

 we find the only authority for the well-developed lungs, carefully 

 explaining in parenthesis that he applies that term for want 

 of a better to that very familiar organ, the swimming bladder. 

 Now this conversion of the swimming bladder of fishes into a lung- 

 like organ is an abnormal, but by no means uncommon, character in 

 fishes, and has attracted the attention and consideration of all our 

 ichthyologists. Cuvier, and in ichthyology we cannot have a higher 

 authority, has particularly noticed this fact in the genus Amia, also an 

 inhabitant of rivers : of this genus, he says, at p. 327 of the second 

 volume of the ' Regne Animal,' that the swim-bladder is cellular, like 

 the lung of a reptile; the fact would appear to be that the swim- 

 bladder of fishes is in some measure the representative of a lung, and, 

 like the lung, can be voluntarily inflated: the walls of this organ in 

 Amia and Lepidosiren become incrassated and cellular, and certainly 

 in this state represent the lung ; but it is not allowable to take this as 

 evidence of the reptilian nature of the mud-fish, unless we make the 

 application of the theory universal, and thus transfer a perfectly 

 normal malacopterygian, which Amia certainly is, to the class of 

 reptiles also. The mud-fish is acknowledged on all hands to possess 

 a perfect apparatus for breathing water ; it has exactly those proper 

 fish-gills which are the characteristic of fishes; and although the 

 external opening is small, this character simply indicates an approach 

 to the viviparous, rather than the spawning fishes. 



The next structural character to which I wish to invite attention is, 

 the dermal envelope ; this it will be seen is completely covered with 

 scales exactly like those of a fish, and on these scales is a lateral line 

 as distinctly and strongly pronounced as in the most typical of the 



