The Zoologist— March, 1869. 1571 



became more distinct. The thin external skin was shed, and the 

 secretion of mncus from the snrface sensibly diminished. During these 

 changes the animal showed an increasing desire to leave the water, 

 often remaining for some time with lis external nostrils above the sur- 

 face, and occasionally making violent struggles to escape. Aided by a 

 heavy rain at night it at last succeeded, and thus put an end to further 

 observations, just at a time when it had lost the generic characters of 

 Siredon and become a true Amblystoma, two forms of Batrachians 

 usually regarded as belonging to distinct families. 



Fortunately, a few days later, several other specimens of various 

 sizes began, nearly at the same time, to show unmistakable indications 

 of a similar transformation, and this afforded an opportunity of noting 

 the successive phases of the change more fully, as well as of observing 

 the physical conditions which seemed to promote or retard it. Two of 

 the specimens were placed in a glass jar, and left in a strong light, 

 and five others were kept in a cooler place in the shade, the tempera- 

 ture of the two, however, differing but a few degrees. At the end of 

 three weeks those in the glass vessel had apparently completed then- 

 metamorphosis, while of the others less favourably situated three only 

 were partially altered, and at the present time, or nearly three weeks 

 later, they still retain tubercular remnants of the external branchiae, 

 although in most other respects the change appears to be complete. 

 The two remaining specimens, however, which had throughout been 

 kept with the three last, showed no distinct signs of changing, although 

 the probability of their doing so, and the importance of retaining some 

 tangible evidence of the original condition, led to the transfer of one 

 of them to a jar of alcohol after the first week, a precaution, as the 

 result showed, quite unnecessary in the case of the other, which at the 

 time of writing (October 5th, 1868) still remains a typical siredon, 

 with no alteration more important than a single appearance in a new 

 epidermis. 



The changes observed in the five specimens that underwent the 

 complete metamorphosis were essentially the same as those noticed in 

 the one already described, although in no two individuals were the 

 successive phases quite contemporaneous or identical. The most 

 marked differences observed were in the colour, both during the trans- 

 formation and after its completion. This was very noticeable even in 

 specimens exposed to the same physical conditions. In the siredon 

 state all were apparently precisely alike in this respect, and the first 

 indications of change detected in each case was the appearance of the 



