THE NUMERICAL ASPECT OF OAK GALLS. 21 
bud, it went on without interruption to another, and 
was altogether eighty-seven hours busily employed in 
laying its eggs. In two buds I counted 582 eggs” 
(‘ Alternating Generations,’ p. 72). 
So accurately are the ova placed either within, or 
upon, the cambium layer, that failure in gall-production 
is rare. 
The operation of ege depositing isa delicate one and 
it demands much care and time. 
When Neuroterus lenticularis settles on a bud, the 
long and slender terebra is inserted near the apex and 
pushed between the leaf-scales down to the base of the 
bud; then it curves upwards, penetrating a part of the 
bud axis, until it comes into contact with that part of 
the embryo leaf which will be the under-surface when 
expanded; the gall of Spathegaster baccarum then 
develops. N. leviusculus, whose mode of oviposition is 
similar, requires from fifteen to twenty minutes to 
perform the same operation. But piercing the vege- 
table tissues is only one part; the egg with its long 
stalk has to be pushed along until it reaches the termi- 
nation of the puncture. For each egg a separate 
tube has to be made in the bud, because the egg-stalk 
occupies too large an amount of space in the tube to 
allow another egg to be pushed by the side of it. 
Efficiency is aimed at by the Cynips, and she is 
rewarded for her labours and care by a high percentage 
of satisfactory results. 
How it is possible for the insect to determine the 
exact spot for the egg to he is beyond the scope of 
the present consideration of the phenomenon, except 
to mention that certain tactile hairlets, whose bases are 
connected with nerves, are situated on the ovipositor, 
which are also employed in the discrimination between 
leaf-buds and flower-buds. 
In comparison with the size of the abdomen the 
ovaries are very large,and many species of the Cynipide 
contain enormous numbers of ova. 
The ovaries of Cynips Kollari have been shown by 
