ON THE ORIGIN OF THE FORMS OF GALLS. 29 



a^ccording to the French Naturalist, a poison peculiar 

 to itself, and it Avas by virtue of this iDeculiarity 

 that each species invariably raised galls of a specific 

 description. Lacaze-Duthiers did not make any 

 investigations into the nature of the liquid secreted 

 by the gland attached to the ovipositor in the 

 gall-flies ; and the only fact which he adduces as 

 showing that there may be a difference, is that the 

 poison of different bees and Avasi)s is not of the 

 same strength with all of them ; for some species 

 sting much more severely than do others. He com- 

 pares the secretion to vaccine matter; just as when 

 the contagium of, say, small-pox, is introduced into 

 the human system, it invariably produces small-pox 

 and not scarlet fever; so the j)oison of Cynips 

 Kollari always gives origin to the ^veil-known 

 marble-galls and not to oak-spangles or oak-apples. 

 This view of the specific nature of the secretion 

 has been strongly supported by Sir James Paget^ 

 the well-known j)atliologist. He says : " In these 

 and other similar diseases in x^l^mts ^\e have, it 

 seems, hundreds of specific diseases due to as many 

 hundreds of specific morbid poisons ; for the most 

 reasonable, if not the only reasonable, theory of 

 these diseases is, that each insect infects or inocu- 

 lates the leaf or other structure of the chosen j)lant 

 with a poison peculiar to itself. The poison may be 

 merely deposited ; but, in the instances best fitted for 

 study, it is inserted in the plant itself, whether 

 leaf or any other, and the wound for inserting it, 

 the poisoned wound, may be made either with ^Dart 

 of the oral apparatus, or, as in most of the true 

 galls, with the ovipositor, through which one or 

 more eggs are passed with the virus, and are left 

 among actively living structures of the plant. The 

 little wound closes, the virus, whether an oral or 

 an ovarian secretion, remains, and the result of its 

 influence in the plant structure and their contained 

 protoplasm is the formation of the gall or other 

 morbid products." Again : " We find hundreds of 



