1908-9.] THE Hasits OF PLETHODON CINEREUS ERYTHRONOTUS. 485) 
of about 6 mm. is reached. When pigmentation does begin it rapidly 
assumes the pattern and colours of the adult; this is evidently related 
to the fact that when the larva issues from the egg envelopes it at once 
assumes the habits and habitat of the adult. The lack of a free larval 
life differing from that of the adult renders unnecessary the distinctive 
larval colouration so common among Amphibia. At the same time the 
surrounding darkness renders it safe for the larva to receive the colour- 
ation of the adult. The reason why the larva of Autodax (Ritter and 
Miller ’09; Ritter ’03) should under somewhat similar circumstances show 
a darker colour than the adult may lie partly at least in the fact that its 
development occurs in dimly lighted cavities and not in absolute dark- 
ness as does that of Plethodon. 
Amblystoma (or Spelerpes), Desmognathus, Plethodon, and Autodax 
form an interesting series the members of which, taking larval and adult 
life together, show an increasing adaptation to terrestrial life. The first 
is terrestrial only in adult life and returns to the water to lay its eggs. 
Desmognathus (Wilder ’99) begins its development on land like Plethodon 
but near the water; it leaves the egg while yet a larva completing its 
development in the water and accordingly stands as an intermediate 
between Amblystoma and Plethodon. The habitat of the adult Des- 
mognathus, never far from a stream, also shows a less degree of adaptation 
to terrestrial life than that attained by Plethodon whose habitat bears 
no relation to bodies of water. On the other hand Autodax is less de- 
pendent on moisture in its surroundings even than Plethodon. I have 
had adult Plethodons die in confinement from conditions of no greater 
dryness than those described as supported by Autodax (Ritter and Miller 
’99). Moreover the prehensile tail, the greater ability in leaping and 
more intelligent use of the power would also indicate more perfect adap- 
tation to terrestrial conditions than has been attained by Plethodon. 
As larva, Autodax has entirely lost the fringed condition of the gills; 
Plethodon still retains these fringes but in such varying degrees in differ- 
ent individuals as to indicate their decadence as organs. The degree 
of parental care of eggs and larve increases regularly in the series Am- 
blystoma, Desmognathus, Plethodon and Autodax. 
EXPERIMENTS. 
To determine what part the mother may play in the incubation 
various plans of development under artificial conditions were tried. If 
removed from their natural surroundings and suspended in air the eggs 
show signs of rapid loss of moisture and the larve soon die. To obtain 
an atmosphere as moist as that in which they naturally hang, clusters 
