1570 The Zoologist— March, J8G9. 



except those of age and sex. They were from five to ten inches in 

 length, of a uniform dark olive, or pistachio-green colour above and a 

 light olive below. The vascular fimbriae of the external branchial 

 appendages, or gills, were black. In form and general appearance all 

 the specimens corresponded essentially with the one represented in 

 fig. 1. They were brought to New Haven alive, apparently without 

 suffering much inconvenience, either from a transfer to fresh water or 

 from the long journey. They all fed readily upon worms and insects, 

 and occasionally came to the surface and inhaled air. More rarely an 

 exhalation occurred, usually under water. On being removed from 

 their native element they soon showed the same signs of distress as 

 fishes under similar circumstances, although in a much less degree. 



The account recently published by Prof Dumeril of the remarkable 

 metamorphosis of the second generation of axolotls {Siredon Mexi- 

 canus) from the table lands of Mexico, while kept in the Museum 

 d'Histoire Naturelle, in Paris,* made it a point of no little interest to 

 determine whether this species also would undergo a similar change 

 when placed under different physical conditions, and hence the speci- 

 mens were watched with considerable care. 



The first indications of any change were observed in one of the 

 smaller specimens, about six inches in length ; and the metamorphosis 

 had apparently commenced during the journey from Lake Como to 

 New Haven, which lasted about a week. Small round spots of dark 

 brown were first noticed on the sides of the tail, and the colour of the 

 entire animal gradually assumed a darker hue. The broad thin mem- 

 brane along the back, and above and below the tail, gradually began 

 to diminish by absorption, the external branchial appendages soon 

 became similarly affected, especially at the ends, and the animal came 

 more frequently to the surface of the water for air. As the change 

 went on the dark spots increased in number and size, and gradually 

 extended over the whole upper part of the body. The membrane on 

 the back and tail entirely disappeared, leaving in its place in the dorsal 

 region a sharp groove. The branchiae also continued to diminish, and 

 at the same time the internal branchial arches began to be absorbed, 

 and shortly after the openings on the neck closed up. In the mean- 

 time the head became more rounded above and more oval in outline, 

 the muzzle narrower and more pointed, and the eyes more convex and 

 prominent. The body also decreased in bulk, and the costal grooves 



* ' Comples Rendus,* loine Ixi., p. 775, 1865 ; and loine Ixv., p. 212, 1867. 



