552 IHE AMERICAN NATURALIST. [VoL. XXXIV. 
Mexican form does so, for it is contended by Cope (89) that all 
of these have been working, not with the Mexican form, or 
“true axolotl,” but with larve of Améblystoma tigrinum. The 
latter have been found in several localities in this country. In 
1852 Professor S. F. Baird described the external features 
of a siredon, called by him .Szredoz lichenoides, from Santa Fé 
Creek, New Mexico, and later, in 1859, the same writer de- 
scribed another, which he called S. gracilis, from the Cascade 
Mountains, near the fortieth parallel of latitude. This writer 
did not observe the transformation of siredon (though he 
conjectured it); but in 1868 Professor O. C. Marsh of Yale 
College collected siredons in a lake in Wyoming, at a level 
of 7000 feet above the sea, and conveyed them to New 
Haven, where they transformed into A. tigrinum.  Teget- 
meyer (70) figures an S. mexicanus, which, while in his posses- 
sion, transformed into an A. tigrinum. It appears from his 
figure to be identical with Baird's S. /ichenoides. In all these 
cases, however, it will be noticed that the siredons were not in 
their normal surroundings, and hence it is not decided whether 
their transformation takes place in nature or whether they 
reproduce while still in possession of the larval characteristics. 
There is a great difference between merely a greatly over- 
grown true larva, one not yet capable of reproduction, and the 
condition of the axolotl in which the reproductive organs are 
matured before the other organs in the other systems have 
reached the form that they have in adult amblystomas. It is 
not impossible that both conditions exist, a siredon in which 
the animal is a true larva not yet matured, and an axolotl in 
which the animal is at once a larva and a mature form. 
In this sense Marsh's specimens would be siredons, and 
Dumeril’s first generation axolotls, and the second siredons. 
After the matter of this article had been made nearly ready 
for the press I had my attention called by Dr. T. G. Lee of the 
Minnesota State University to a collection of about twenty- 
five specimens of an axolotl which seems to be very similar to 
Marsh's S. mavortium, and which were found by him in an 
alpine lake in Montana. Dr. Lee has most generously placed 
all of this material (which is splendidly preserved in formalin) 
