No. 387.] DESMOGNATHUS FUSCA. 243 
to the former species. This may become a certainty if the larva 
be above 35 mm. in total length. At about 20 mm. the larve 
of D. fusca have very small external gills, and the tail fin is 
obsolescent; while larvæ of S. bilineatus of the same size have 
very apparent external gills and a very broad tail fin, ending 
obtusely. In general, the larva of D. fusca is at all stages 
suggestive of maturity, while that of S. bilineatus is larval 
and piscine in its general appearance. The former resembles 
Amblystoma in shape, the latter Necturus. The former has a 
25 
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16 20 24 28 32 36 40 44 48 52 
Fic. 26. — Curve showing frequency of the larva of S. d¢/ineatus at its different stages. 
short head, rounded above, shows well-marked costal folds, has 
robust limbs and a narrow tail fin. The latter has a long flat 
head, obscure costal folds, and a very broad tail fin. A definite 
distinguishing characteristic does not seem to exist, but there 
are so many general distinctions that a person who has once 
studied and compared the two will find no difficulty in identify- 
ing each species at any stage. 
Method of Rearing in Confinement.— The adults of both 
species, because of their peculiarities in respiration and the 
consequent necessity of keeping their skin moist, cannot be 
kept either in water or in a dry atmosphere, but may easily 
