METAMORPHOSIS OF THE AXOLOTL. 413 



Heplaced in deep loater. 



StMge 5. March 6th. 



„ 6. March 13th. 



„ 7. March 19th. 



„ 8. March 27th.— Length 113 mm. 



Specimen JS^o. 10. 



Placed in shallow water at a temperature of 55°-60^. 



Stage 1. October 7th. — Length 105 mm. 

 ,, 2. October 31st. 

 ,, 3. November 30th. 



Died March 24th. — Length 105 mm. 



Specimen No. 11. 



Placed in foul water from which the oxygen was removed 

 by the gradual addition of boiled water. 



Stage 1. October 7th. — Length 112 mm. 

 Died March 22nd. „ 120 mm. 



The results of these experiments show, I think, in the first 

 place that, in accordance with Mile, de Chauvin's observations, 

 and contrary to those of Dr. Powers, the Mexican Axolotl will, 

 with perhaps a few exceptions, transform into the Amblystome 

 stage if placed, when about six months old, under conditions 

 which force it to make frequent use of its kings ; secondly, that 

 starvation, irregular feeding, and temperature have no influence 

 on the metamorphosis ; thirdly that, as no change occurs when 

 the Axolotl is placed in poorly oxygenated vi^ater, owing to the 

 fact that it will not under the circumstances rise to the surface 

 and make use of its lungs, the quantity of oxygen in the lakes 

 of Mexico can have little bearing on the explanation of the 

 phenomenon of neoteny ; and lastly, that there is a critical stage 

 in the metamorphosis. 



References. 



1. A. DuMERiL. — Comptes Rendus, Ix. (1865), and Nouv. Arch, 



Mus. ii. (1866). 



2. A. Weismann. — Zeitschr. wiss. Zool. xxv. (1875). 



3. Mlle. de Chauvin. — Zeitschr. wiss. Zool. xxvii. (1876). 



4. J. H. Powers. — Amer. ISTat. xxxvii. (1903). 



5. H. Gadow.— Nature, Ixvii. (1903). 



