478 TRANSACTIONS OF THE CANADIAN INSTITUTE. | (Vor. VIII. 
25mm. A similar condition is found in Amblystoma, Rana and other 
amphibia where the eggs are laid in clusters; the cause being the difficulty 
with which respiration is carried on in the central eggs. 
Escape from the mucous envelope occurs when the larva has reached 
the length of 20 to 25 mm.; this is about the first week of September. 
The outer larve of a cluster escape first but remain with the mother 
beneath their less developed brethren. Respiration is now more perfect 
in these; in a few days their gills have dissappeared and they also escape. 
However the interval does not suffice to bring them so far on in develop- 
ment as were the outer ones when they escaped; they have absorbed 
less yolk and are shorter. They also seem unfit to come in competition 
with their more favored brethren of the outside of the bunch of eggs, 
their movements being comparatively feeble and ineffective; many of 
them probably die. Thus is supplied another factor tending toward 
the production of small numbers of large eggs; for those young will be 
best fitted for life that come from broods where all the nourishment 
available as yolk is divided among but few eggs, so few that none are 
crowded into the centre of the cluster. 
The family does not scatter at once, an unusual thing among Urodeles 
that have attained their adult form, but accompanied by the mother, 
perhaps led by her, the brood leaves the interior of the log to live beneath 
stones, fragments of wood or bark, lying on the surface of the ground, 
or even among layers of mouldering leaves. If not disturbed when 
uncovered the young will be found in contact with the body of the mother, 
probably to obtain moisture; for the localities in which they now are 
contain little moisture at this season of the year. ‘The families do not 
hold together for long. In the latter part of September a few solitary 
young will be found and early in October all the broods seem to have 
broken up. The rate of growth in Plethodon must vary enormously 
in different individuals, for at this season it is easy to collect a series 
beginning with young accompanying the mother and ending with full 
grown specimens, the increase in size being so gradual that it is impossible 
to draw with certainty a line between this year’s and last year’s broods. 
Apparently the ability to withstand the winter is independent of size for 
early in May an occasional specimen will be found that is little larger 
than the young at the time they escape from the egg—that is less than 
30 mm. in length. 
The following description of the external appearance during develop- 
ment is based upon the examination of over 170 embryos that had been 
fixed in Zenker’s fluid and preserved in 80% alcohol, the members of each 
