Fishes. 



6459 



spawning fishes. Dr. Gray, naturally anxious, of course, to explain 

 away so decidedly an ichthyac character as the possession of a lateral 

 line, which had previously been pointed out by M. Dumeril, and also 

 by myself in a paper read before the Linnean Society, makes use of 

 the following words : — " Authors have laid great stress on the fact of 

 its being provided with a lateral line, overlooking the fact that the 

 common eft {Triton cristatus) has similar lines on both the sides and 

 head/' Now, has not Dr. Gray overlooked the fact that the lateral 

 line of fishes is on the external surface of the scales, and that am- 

 phibians being destitute of scales cannot by any possibility possess the 

 true ichthyac lateral line ? Dwelling for another moment on the very 

 complete armature of scales with which the mud-fish is covered, it 

 must be remarked that this character alone is quite sufficient to 

 separate it from the Amphibia, which are, without exception, totally 

 destitute of scales; indeed, almost every naturalist has made this a 

 leading character in distinguishing the spawning from the oviparous 

 reptiles : the possession of scales, and the lateral line on those scales, 

 are both of them unmistakeable proofs that Lepidosiren is a fish, and 

 not an amphibian. 



Lastly, let us make a transverse section of the body of the mud- 

 fish, and we find its vertical diameter incomparably the greater as in 

 fishes, while in reptiles, including the amphibians, a contrary cha- 

 racter obtains, the transverse diameter being invariably greatest. I 

 think that no attempt can be made to associate the mud-fish with 

 the isogenous, oviparous or scaly reptiles, because the only reptilian 

 character it possesses are those of the true amphibians ; indeed no 

 one has assumed the existence of any affinity between the mud-fish 

 and the oviparous reptiles. Allow me then to recapitulate the cha- 

 racters in which it differs from the amphibians. 



1st. Its rythmical breathing and its mode of taking atmospheric 

 air at the surface of water, when the oxygen of the water in 

 which it has been kept is exhausted. 



2nd. Its velocity in swimming, as particularly pointed out by 

 Mr. Hawkins and Mr. Bartlett. 



3rd. Its mode of eating. 



4th. The composition of, as well as the mode of using, its four 



extremities. 

 5th. Its scaly covering and lateral line. 



6th. The greater diameter of a vertical section of its body com- 

 pared with a transverse section. 



