DEGRADATION OF ORGANISATION 79 



which have legs, are more degraded in organisation and nearer to the 

 fishes. 



The proofs of the important principle which I am stating will be 

 based upon positive facts ; they will consequently always hold good 

 in contact with the arguments that are brought against them. 



FISHES. 



Animals breathing by gills, with a smooth or scaly skin ; the body 

 ^provided with fins. 



On following the course of that degradation undergone by organisa- 

 tion as a whole and of the diminution in the number of animal faculties, 

 we see that the fishes must of necessity be placed in the fourth rank, 

 that is, after the reptiles. Their organisation in fact is even less 

 advanced towards perfection than is that of reptiles, and is conse- 

 quently more remote from that of the most perfect animals. 



It is true no doubt that their general shape, the absence of a con- 

 striction between the head and body to form a neck, and the various 

 fins which for them take the place of limbs, are results of the influence 

 of the dense medium they inhabit, and not of the degradation of 

 organisation. But that degradation is none the less real and very 

 great, as we may convince ourselves by an examination of their 

 internal organs ; so that we are forced to assign to fishes a lower 

 rank than to reptiles. 



We no longer find in them the respiratory organ of the most perfect 

 animals ; for they have no true lung, and in its place have only gills 

 or vascular pectinate folds arranged on both sides of the neck or head, 

 four altogether on each side. The water which these animals breathe 

 goes in by the mouth, passes between the folds of the gills, and bathes 

 the numerous vessels which run there. Now since the water is mixed 

 with air or contains it in solution, that air although small in quantity 

 acts upon the blood of the gills and there achieves the function of 

 respiration. The water then issues through open holes on either 

 side of the neck. 



Note that this is the last time that the respired fluid enters by the 

 animal's mouth in order to reach the organ of respiration. 



These animals, like those of the posterior ranks, have no trachea 

 or larynx or true voice (including even those called grondeurs ^) 

 or eyehds, etc. These organs and faculties are here lost and are not 

 again found throughout the animal kingdom. 



Yet the fishes are still part of the division of vertebrate animals ; 

 1 [The Grey Gurnard. H.E.] 



