10 BRITISH OAK GALLS. 
egg is laid within or upon its tissues no gall formation 
takes place. Taking this, therefore, as the main 
feature upon which gall formation depends, it will 
not be difficult to trace a few leading characteristics 
relating to the development, environment, aberrations, 
etc., in British oak gall growth. 
They may be tabulated as shown on ‘page 9. 
Duration oF Growrs. 
(a) Rapid ; a few days. 
The periods of duration of growth are either very 
short or protracted. In point of rapidity probably no 
other oak gall develops and reaches maturity with 
such speed as does Spathegaster Aprilinus. Under 
ordinary conditions three or four days are sufficient 
for it to be completely formed and reach its maximun 
of size. Spathegaster baccarum, S. tricolor and Trigon- 
aspis crustalis are about equal with each other in the 
same respect, and either may be mature within seven 
or eight days. This does not imply that the inhabitant, 
or inhabitants, have passed through the metamorphoses 
and the imagines ready to emerge, although in the 
case of 8. Aprilinus only a few days more are required 
for its accomplishment. 
(b) Slow ; several months. 
The gall of Cynips Kollari doubtless requires a longer 
time to attain maturity than any other. Beginning 
growth early in April, it steadily progresses until 
September before it ceases. But C. Kollar is a gall 
by itself. It has been described as neither catkin, 
leaf, bud, nor stem gall, belonging, indeed, to another 
and separate category. 
Aphilothriz radicis is the next slowest in growth, 
five months being occupied in its development. Its 
persistency and protracted decay are about equal to 
those of C. Kollavi, extending to two or even three 
years. 
