448 Dr. V. Fatio on the Variability of the 



In these two instances a too rapid change of conditions 

 leads to a rupture in the equilibrium of the organism, and often 

 involves the death of the individual. The elastic fibres of the 

 air-bladder, too rapidly distended, can no more resume their 

 empire and exert a sufficient compression ; and this would not 

 have happened in consequence of slower and more gradual 

 transitions. 



But the principal purpose of the air-bladder is not, appa- 

 rently, to condemn the species to an invariable habitat ; the 

 function of this organ is rather, by pressing against the back- 

 bone, to keep the individual in the normal position proper for 

 its preservation. Other examples will enable us to understand 

 the importance of this function from the point of view of the 

 preservation of the deviated race, and the comparative action 

 either of certain organs of relation upon the bladder, which is 

 at once a moderative agent and one of equilibrium, or of the 

 latter upon the position of the individual, and thereby upon 

 some of its external forms. 



Every one is acquainted with the goldfish or gold carp 

 {Carassius auratus)^ which normally exhibits oblong forms 

 like those of the carp, but to which tlie Chinese have found the 

 way to give the most curious shapes. By cleverly taking 

 advantage of th"fe smallest accidental deformations, and insti- 

 gating and exaggerating monstrous tendencies by subjecting 

 the fish to abnormid conditions, the adroit inhabitants of the 

 celestial empire have actually succeeded in manufacturing 

 goldfish with double and triple fins, with a quasi-spherical 

 body, and with the eyes excessively prominent, or often borne 

 upon a longer or shorter pedicle *. 



M. Carbonnier, of Paris, has already remarked that the 

 equilibrium is very unstable in the quasi-globular varieties of 

 the goldfish, and that, after arriving at a certain age, many of 

 the young fishes of this form must perish, from being forcibly 

 kept in a position which scarcely allows them to feed, some 

 of them with the head turned upwards, many with the head 

 turned down. Two years ago I had the opportunity of seeing 

 in the aquaria of this learned observer several adult globular 

 goldfish with more or less prominent eyes, in which the very 

 different arrangement of the mouth particularly attracted ray 

 attention. Two of these appeared to me to be especially 

 interesting. 



One of them, with a spherical form and a comparatively 

 short backbone, presented a very turned-up snout and a very 



* It is believed that this last variety, which has received the name of 

 the telescope-lish, may be produced by causing the light to reach the 

 fish only from a single point. 



