804 THE AMERICAN NATURALIST. [Vor. XXXIV. 
within the scales but near the tip of the leaf, they did not give 
rise to larvae that matured, because, as will be shown later, the 
young larvae were not in contact with living tissue which could 
give them nourishment. The larve take their food only by 
absorption through the surface of the body. This makes it 
essential for them to be in contact with living cells, from 
which the necessary 
food matters can be 
abstracted. This con- 
dition, namely, that 
the larvae must be in 
physical contact with 
tissues which will give 
them food, is fully 
b J ‘realized only when the 
f eggs from which they 
/ develop are placed at 
Fic. 2.— A, longitudinal section of a leaf fascicle with eggs the bases of the inner 
placed at the base of the leaves and of the i protecting scales. It is conse- 
scales ; one egg is also shown between the scales. X 28%. 
B, longitudinal section showi f eggs at the base quently necessary that 
TM TOME the distance from the 
tip of the needles, or in other words the length of the leaves, 
be approximately the same as the length of the ovipositor of 
the fly, for only in this way can the eggs be so placed that the 
larvae which result from them will live. This exacting condition 
we find is complied with by most of the leaf bundles of the 
Monterey pine during the month of February, or during the 
season of the gallfly’s activity. 
by 
mn 
5 
IE; 
All of the young leaves grow rapidly in length during the 
month of March, and the first week in April most of them are 
approximately 1 cm. long ; thus, they have increased about five 
times in length in somewhat over four weeks (Fig. 3). UP 
to the first of April there is no apparent difference between the 
normal and the galled leaves; from this time on, however, the 
difference in length and diameter between the affected and 
