1908-9. | THE Hapits OF PLETHODON CINEREUS ERYTHRONOTUS. ‘475 
-drical form of body (the proportion of length to greatest breadth being 
fourteen to one) in an animal so small, along with the necessity for pro- 
ducing eggs containing a large amount of yolk are doubtless factors | 
determining the small number of eggs; another will be mentioned later. 
The necessity for the large amount of yolk in the egg arises from the 
purely terrestrial development of the larva. Aquatic larve have at 
command the minute and abundant fresh-water plankton as food supply 
and are thus at an early age rendered independent of the nourishment 
provided in the yolk. The insect life that constitutes the early food of 
the terrestrial Plethodon is of larger size than much of the plankton 
and much less abundant. Consequently the animal on leaving the egg 
must be able to wait for food through comparatively long intervals 
and also to capture food of larger size than an aquatic larva need 
do. Both of these things demand an advanced development that can 
only occur when a considerable quantity of yolk is provided. 
Each egg is surrounded by a series of mucous spheres as is customary 
in Urodeles. In their natural condition the number of these is rather 
difficult to determine but after soaking a few minutes in water they swell 
somewhat and the following is plainly seen:—an innermost sphere very 
close to the surface of the egg; a second enclosing this but separated 
from it by a greater interval than that between the innermost sphere 
and the egg; occasionally this sphere is represented by two, one of them 
fitted very closely around the other. The outermost sphere—usually the 
third—fuses with the outermost spheres of neighboring eggs at all points 
of contact. On its surface are threads and bands of a milky white mucus 
which seems tougher than the rest, which is transparent; these are es- 
pecially numerous between eggs and at the upper part of the bunch where 
several uniting form the stalk by which the cluster is suspended. This 
mode of attachment is probably derived from one originally like that 
of Desmognathus (Wilder ’99) in which each egg of the cluster is inde- 
pendent of all the rest and has its own cord joining it to the common 
stalk. The tension of the envelopes, especially the innermost, is needed 
.to preserve the spherical shape of the egg. These envelopes are very 
tough; a weak hypochlorite solution will soften them so that they can 
be removed but when their support is gone the egg, even in water, flattens 
until the vertical diameter is little more than half the transverse. In 
the younger stages it is therefore necessary to fix and harden the egg 
first and remove the membranes later, they should be removed as soon 
as possible for if left around the egg the latter will in time disintegrate. 
The method devised by Morgan (’91) has proved the most satisfactory. 
As development proceeds the amount of fluid between the egg and 
