1102 The American Naturalist. [December, 
In Diemyctylus this mixed respiration and the food supply 
apparantly proved so satisfactory that the aquatic life again 
became fixed, and, acting through numberless generations, the 
tendency to revert to aquatic life became so great that maturing 
forms sometimes enter the water at least six months before the 
breeding season (Kelly, ’78). It does not, however, revert so 
completely to an aquatic life that it cannot, in case of necessity, 
again become terrestrial for a considerable time. 
This permanent reversion to a primitive mode of life by 
Diemyctylus does not stand alone among the Batrachia. It is 
paralleled and even exceeded by Siren, which after passing 
through the ordinary larval metamorphosis, has its gills so far 
absorbed as to be mere stubs. It then not only returns to the 
water, but actually reacquires its gills (Cope, 85). These two 
cases seem to point to the conclusion that in the course of evolu- 
tion: the dangers and hardships of the land became equal or 
greater than those of the water for these forms, and they, by read- 
justing themselves to an aquatic life, rendered the struggle for 
existence less severe. Certainly there is no reason, in the funda- 
mental idea of evolution, why an animal may not revert to an 
earlier condition, provided it becomes as markedly to its advan- 
tage as was the original departure from that condition. 
Summary—t. The red and the viridescent forms of Diemy- 
ctylus belong to the same species, the red form being an immature 
condition, 
2. The ova of Diemyctylus are internally fertilized, and are laid 
singly on a submerged leaf, or between submerged leaves, and 
partly concealed by folding the leaves closely together. If no 
leaves are available, the eggs are laid on stones or bare stems. 
The eggs hatch in about thirty days. 
3. In from three to four months after hatching, vermilion spots 
appear, and are symmetrically arranged along the dorsal aspect 
next the head. The general appearance is then strikingly like 
that of the adult male in the breeding season, except that the 
tail crest, instead of ending opposite the pelvis, extends nearly or 
quite to the head, as in the crested Triton. Later, gills and tail- 
fin atrophy, and the respiration becomes more and more aérial. 





