SOME FEATTIIIES OF OAK GALL GKOWTH. lo 



difficult to determine. The larval cell of Andricu.s 

 curvator is also occasionally somewhat reniform. 



(d) Lenticular. — This form of growth is confined to 

 the three leaf spangles, and in N. lenticularis and 

 N. fwmipennis it is very constant, except when the 

 galls are over-crowded. N. laeoiusciilnx, 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. Kollari. On 

 Plate XXXVI a numljer 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 larvae 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 89 are scarcely recognisable as double 

 galls, yet each contained two larvse; so also does Fig. 40 ; 

 a slight division is, however, noticeal)le. Figs 23-28 

 are double, but of very consideral)le unequal develop- 

 ment, showing that one larva lived for a short time 

 only. Figs. 29, 30, 33-17, 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 



