Sijecies in the case of certain Fishes. 449 



oblique mouth ; it could hardlj take any food, except above 

 it or at the surface of the water. The other, which was also 

 globular and had a very oblique mouth, but with a still 

 shorter backbone, remained completely turned over on its 

 back, with its large belly upwards. The latter, it seems, had 

 commenced by being like the other ; then, at a certain 

 moment, the air-bladder being more and more displaced by 

 the pressure of the vertebral column, and the centre of gravity 

 shifted, the animal was completely turned over. 



It appeared that the reversed goldfish, when food was 

 offered to it after a long fast, could still take nourishment by 

 great exertions, and that, under the influence of this tempo- 

 rary counterpoise in the digestive tube, it could maintain itself 

 for a certain period, and by considerable efforts, in a quasi- 

 normal position, but only to allow itself soon afterwards to be 

 turned upside down again by the air-bladder. 



In consequence of a compulsorily ahno7vnal position ^ the head 

 and then the backbone had gradually been deformed, until the 

 arrival of a moment when, the equilibrium being broken and 

 the fins being unable any longer to struggle sufficiently, the 

 air-bladder intervened to put a forced term to the primary 

 external modifications. 



I have for some time observed, in one of the aquaria of M. 

 E. Covelle at Geneva, a very curious pathological case, to a 

 certain extent parallel to that of the goldfish, in an adult rudd 

 {Scardinius erythrophthalmus). For about three months this 

 fish has remained at the bottom of the aquarium, always lyino- 

 upon its right side. The air-bladder, which can no longer 

 press against the backbone, now forms a very apparent 

 swelling upon the left side. In consequence of a paralysis 

 produced, after a fall, in the anterior dorsal muscles of the 

 right side, there took place, by degrees, first an increasing 

 atrophy of the above-mentioned right lateral muscles, and 

 afterwards a gradual deviation of the vertebral column. At 

 present the paralysis has reached the level of the ventrals, and 

 the caudal portion of the body is recurving by little and little 

 towards the back. Nevertheless this fish can still, by great 

 exertions, like the reversed goldfish, take and digest the food 

 that is put from time to time within its reach. Although 

 meagre, it appears to be in very good health, except for its 

 paralysis ; its respiratory movements, although rather rapid, 

 are comparatively normal ; and the free pectoral fin, during 

 this compulsory repose, nevertheless moves continually, as if 

 to ventilate the branchiae or agitate the water in the vicinity 

 of those organs. The coloration of the body and fins is per- 

 fectly good, and does not seem at present to indicate any 

 impoverisliment. 



