19H] Smith, Natural History of Ambystoma. 17 



protection during the winter, so well as the matted vegetation 

 and deep mud of portions of the pond itself. It seems quite prob- 

 able that, in the case of A. tigrinum at least, migration is an 

 event depending somewhat upon ecological conditions. 



THE SPAWNING SEASON. 



As shown by the study of the two species of Ambystoma 

 occurring together in Branchipus Pond, the spawning season of 

 A. jeffersonianum is distinctly earlier than that of A. punctatum. 



In 1909 the first eggs of A. jeffersonianum were found on 

 April 5 ; the first eggs of A. punctatum on April 13. The precise 

 duration of the spawning season was not determined, but no 

 fresh eggs of either species were found after April 16. 



At Ann Arbor newly-laid eggs of A. punctatum were found 

 on April 1, 1905, and April 9, 1906. I have no records for first 

 appearances of eggs oiA. tiginum in this locality, but my general 

 impression is that the spawning season is slightly earlier than 

 for A. punctatum. At Lake Forest the first record of eggs for 

 A. tigrinum in 1907 is March 19, and the last for newly-laid eggs 

 is April 4, the spawning season having been interrupted by a 

 week of cold weather. At Madison in 1910 the first eggs of A. 

 tigrinum were found on March 26 ; they were in early segmenta- 

 tion stages. 



THE ADULTS. 



Ambystoma jeffersonianum (see Plate I, Fig. 1) is usually 

 covered with small white spots, irregular in size and distribution ; 

 in some specimens these are almost entirely absent. 



In its natural habitat, A. punctatum (see Plate II, Fig. 3) has 

 spots of a brilliant yellow ; in captivity, exposed to light, the color 

 fades to a dull yellow ; in formalin it is changed to a dull gray. 



When captured in the early spring, and kept for a few days 

 in confinement, all three species shed the cuticle, usually intact 

 or nearly so. The most perfect specimens of entire shed cuticles 

 were obtained in 1907 from A. tigrinum. Four shed cuticles 

 were obtained from the same number of specimens in captivity, 

 and of these three were intact, one broken into two pieces. All 

 were turned almost completely wrong-side out. The cuticle is 



