68 University of California Publications in Zoology [Vol. 27 
in the hope of observing earlier stages of development, but the season 
had been enough earlier that the larvae were nearly of the same size 
as those obtained in 1922, as they measured from 35 to 48 millimeters 
in length. On March 14, 1923, a pool in the foothills about 4 miles 
south of Lagrange, Stanislaus County, was found to contain many 
larvae ; a sample lot of these measured 28 to 47 millimeters in total 
length. On May 14, Mr. Snook obtained many large larvae from a 
pool in Victory Park, Stockton. Some of these were already under- 
going metamorphosis on the date mentioned. Five of the larvae were 
sent to the writer and four of them metamorphosed within ten days, 
while the fifth, kept under identical conditions, was still in the larval 
state on June 26, 1923. 
The larval period is short, probably less than four months. Con- 
tinuance as larvae until a large size is reached would be impossible in 
most of the ponds in which the species has been observed in California, 
as these ponds go completely dry in the summer months. Whether 
the larvae in other localities metamorphose at small size is not known. 
Osborn in discussing the anatomy of some large “axolotls’ 7 from Colo- 
rado says that in addition to the large animals which were found in a 
lake near Crede, “Ordinary larvae of Ambly stoma tigrinum ranging 
in length from one to four inches [were present] in the irrigating 
ditches ... in the San Luis Valley in the vicinity of. Garrison” 
(Osborn, 1901, p. 888). 
The larvae of Ambystoma calif orniense are exceedingly wary. In 
the pools near Bellota and Lagrange I found that great caution was 
necessary in order to discover and capture them. When not molested 
or frightened they will often rest lightly on the bottom in shallow 
water (from 2 to 8 inches in depth) and in deeper places will remain 
suspended at this or lesser depths. When resting quietly the gills are 
extended backward and upward in smooth curves, and the limbs and 
digits are extended laterally. At the first hint of danger, such as a 
quick movement on the part of a person, either above or under the 
surface of the water, the gills are pulled down flat against the body, 
the limbs are drawn backward along the sides, and the larva, propelled 
by rapid undulations of its tail and the broad fins attached thereto, 
darts toward the bottom where it hides under bottom vegetation. The 
combination of flat head and vertical tail fin joined to a tapered body 
corresponds to the equipment of a submarine boat, and the rapid 
course is readily guided by appropriate bending movements of the 
