List of the Insect Fauna of the (Jountij. Ill 



in natural history. And I am sure, from all I know of 

 natm-alists, that they will gladly let any of you into their 

 fields, though you may use them for your own purposes much 

 more than for theirs. It would be difficult to find a field for 

 the study of the very principles of pathology larger or richer 

 than this offers to you. The objects are within easy reach ; 

 hundreds of morbid processes are at hand for deliberate study ; 

 experiments may be made at will; during many months, 

 thousands of insects, as natural vivisectors, will be at work 

 for you, and it must yet be some years before they will be 

 required to take out licences." [Ojj. cit., pp. 20 — 28] . 



With these pregnant suggestions, I now leave the origin 

 and growth of galls, and pass on to the insects which produce 

 them ; but once again expressing the opinion that mechanical 

 irritation rather than the action of a specific virus is the pro- 

 bable explanation of gall-growth. 



The vegetable-structure of the various galls deserves a 

 separate memoir, and I leave this in the hands of some of 

 our botanical members, contenting myself with referring 

 them to the following important articles by Meyen,^^ Lacaze- 

 JDuthiers,!^ PriUieux,!^ Beijerinck/^ Courchet,^'' and Frank.^i 



16 Meyen, ' Pflanzen-pathologie ' (1841), divided into :• — 'Auschwellungen,' 

 Odemata, pp. 63 — 65 ; ' Blasenformige Auftreibungen,' Emphymata, 

 pp. 65 — 66; 'Fleischgewachse,' Sarcomata, pp. 66 — 68; ' Gallapfel,' 

 Gallffi (on oaks chiefly), pp. 68 — 71. There is also a French version, 

 ' Traite de Pathologie Vegetale.' I have not been able to find the works 

 either in the libraries at British Museum, Kew, or the Linnean Society. 



17 ' Kecherches pour servir a I'histoire des Galles,' par M. Lacaze- 

 Duthiers. 'Annales des Sciences naturelles,' Botanique, 3rd Series, vol. 

 xix., pp. 273—354 ; pi. 16—19 (Paris, 1853). 



18 'ietudes sur la formation et le developpement de quelques Galles,' 

 par M. Ed. Prillieux. ' Annales des Sciences naturelles,' Botanique, 6th 

 Series, vol. iii., pp. 113—137; pi. 16—18 (Paris, 1876). 



I'J ' Bijdrage tot de Morphologic der Plantengallen.' By M. W. Beijer- 

 inck. 92 pp. and 2 plates (Utrecht, 1877). 



'■^^ ' Etude sur les Galles causees par des Aphidiens,' par M. L. Courchet. 

 ' Academic des Sciences et Lettres de Montpellier ; Memoires de la section 

 des Sciences,' vol. x., pp. 1—102 ; pi. i.— vi. (Montpellier, 1881). 



21 Frank's 'Die Krankheiten der Pflanzen.' Breslau, 1881. For galls, 

 see pp. 661 — 798. 



