SOME FEATURES OF OAK GALL GROWTH. 13 
difficult to determine. The larval cell of Andricus 
curvator is also occasionally somewhat reniform. 
(ad) Lenticular—This form of growth is confined, to 
the three leaf spangles, and in N. lenticularis and 
N. fumipennis it is very constant, except when the 
galls are over-crowded. N. leviusculus, however, 
departs from the true lenticular shape to a consider- 
able extent. 
(e) Aberrations.—Deviations from normal conditions 
of both shape and situations. 
The most remarkable examples of aberrations in oak 
gall growth are found in specimens of C. Kollavi. On 
Plate XXXVI a number of unique specimens are repre- 
sented. Double, triple, and quadruple galls are due to 
two, three, or four eggs being deposited in the same 
leaf-axil, the distance between each being so slight that 
as soon as the larve hatch they are in close contact, 
and although they may each form a cell they are but 
slightly separated from one another. Sometimes they 
interfere with each other’s growth, and then only 
one will survive to pupate. But supposing that all 
reach the imago stage they may not all succeed in 
emerging. One or more may commence to gnaw in 
the direction of the longest axis and not have sufficient 
endurance to reach the exterior, perishing in the 
attempt to eat through double the normal amount of 
gall substance. 
Figs. 38 and 39 are scarcely recognisable as double 
galls, yet each contained two larve; so also does Fig. 40; 
a slight division is, however, noticeable. Figs 23-28 
are double, but of very considerable unequal develop- 
ment, showing that one larva lived for a short time 
only. Figs. 29, 30, 33-47, 41, 42 all have a well- 
defined constriction. All these specimens were attached 
to the twigs at a point immediately above the figures. 
But in Figs. 31, 32, 43, and 44 one sphere only is in 
connection with the twig; the other sphere is united 
to the opposite pole in a Siamese-twin union. They 
are distinct from the common double form. In each 
