The Ecology of a Sheltered Clay Bank 251 
lutely and blindly by instinct, yet they do modify their 
behavior according to their needs. Whether the sun- 
shine is likewise warming the lizards, or whether the 
appearance of possible food excites them, I do not know, 
but at any event these vertebrates, heretofore sluggish, 
become animated and active at the same time as the re- 
mainder of the inhabitants. 
“‘September 23. Only a few stragglers representing 
some of the more important groups of the inhabitants, 
remain at this late date, and they are indeed few in 
number. It is evident that the cold of autumn is a fac 
tor in reducing their numbers, but we should like to 
determine precisely to what extent this is the deter- 
mining factor, or in how far the weather conditions 
directly influence their longevity. If the optimum con- 
ditions for their existence prevailed for several months 
longer, it might retard but would not abolish their mor- 
tality. In other words, to what extent is longevity in- 
herent in the organism, and how far is death due to 
some external calamity? 
“October 3. Today the most of the few individuals to 
be seen certainly give one the impression that they have 
outlived their allotted time—‘yet is their strength labor— 
and sorrow.’ Three survivors of EZ. taurea linger help- 
lessly about, as if they had been overlooked by death 
and did not know how to conduct themselves in the land 
of the living, where they no longer belong. Indeed no 
activity is now possible for them, because the flowers 
from which they have gathered pollen are long since 
withered. Two Ancistrocerus fulvipes mothers are 
feebly finishing the closure of their nests. Two or three 
Monobia mud-wasps are seen on the rafters above the 
bank, stunned and half dead with the cold. The only 
