1911] 



Smith, Natural History of Ambystoma. 



2G 



C. SEVENTEEN DAYS AFTER HATCHING. 



Characters. 



Balancers 



Color pattern 



Front limb rudiment. 

 Hind limb rudiment. 



A. jeffersonianum. 



Lost (about 14 days 

 after hatching). 



Spots sometimes pres- 

 ent. 



With three digits. 



Beginning, no digits. 



A. punctatum. 



Lost (15-18 days). 



No spots. 



With four digits. 

 Beginning. 



D. ONE MONTH AFTER HATCHING. 



Characters. A. jeffersonianum. 



Form of body Usually stouter than 



punctatum. 



Color pattern j Spots sometimes per- 

 sist. 



Front limbs Well developed. 



Hind limb rudiments. .. Much variation in size 



and degree of devel- 

 opment. 



A. punctatum. 



Usually more slender 

 than jeffersonianum. 

 No spots. 



Well developed. 

 Much variation as in 

 jeffersonianum. 



Month-old specimens taken from their natural environment 

 are usually much further advanced than those of the same age 

 reared in the laboratory. 



I have had no opportunity to rear larvae to a greater age 

 than five weeks, but have captured specimens from the aquatic 

 habitats of all three species at various dates during the summer. 

 I feel confident that, in the light of the experience gained with 

 earlier stages, these larvae can easily be assigned to their proper 

 species. 



The late larval stages of A. tigrinum have been described and 

 figured by Powers ("07). with particular attention to the variation 

 in form due to different environments. All the larvae that I have 

 classified as A. tigrinum show a characteristic tadpole-like form 



