1893. ETIOLOGY OF VEGETAL GALLS. 363 



proper occupants — of necessity result ? In my long experience, how- 

 ever, no facts confirmatory of this view have been discovered ; nor is 

 it probable that, under any conditions, such barren galls exist. Are 

 we not then justified in discarding the hypothesis of a specific virus 

 deposited by the parent cynips, and in attributing to the activities of 

 the living embryos, combined, of course, with the normal forces of the 

 plant, the genesis and metamorphosis of the gall ? 



Dr. Ransom, in his address as President of the Section of Medicine 

 at the recent meeting of the British Medical Association at Notting- 

 ham,^^ defined a gall as a local hyperplasia due to the reaction of living 

 cells to irritation. There were no grounds, he said, for adhering to 

 the view, once held, that the parent insect deposits a virus with the 

 egg. No galls were known to be due to any single act or impulse of 

 any kind. The character of the reaction varied mainly with the 

 irritant, but also, in a much less degree, with the tissues irritated. 

 The irritant might inhere in the embryo in ovo, or in the free- 

 hatched larva, or in both, or perhaps in an adult gall-mite, or in a 

 mycelium, or in other more imperfectly understood organisms, animal 

 or vegetal, if living ; and although he granted the possibility that it 

 was sometimes mechanical or physical, yet he thought it more pro- 

 bably always in some organic liquid, chemical substance, not very 

 diffusible, produced in small quantities either continuously or at short 

 intervals during a part of the life and development of the parasite, and 

 having a different composition in each species. 



Resting, as I think we may now do, on this solution of the 

 problem, let us pass from the further consideration of the gall, to that 

 of the gall-producing insect and its parasites '9 ; and here we are met 

 by one of the most curious episodes of entomological science, with a 

 condition of things which, if not proved to be true, might well be 

 regarded as a mere day-dream of the imagination. Nothing, in the 

 prosecution of studies such as these, is more calculated to arrest 

 attention or excite astonishment than the strict balance which is 

 preserved in Nature among the various orders of animated beings. 

 This is especially so with legard to the Insecta. Countless millions 

 of insect-forms continually make their appearance upon the stage of 

 existence, millions equally innumerable as constantly perish — " Comme 

 si " (as Leon Dufour has said), " Comme si, dans le but des harmonies de 

 la Nature, uneloi de destruction devait contre balancer une loi de pro- 

 duction" — as if the end of the harmonies of creation was, that a law of 

 destruction should counterbalance a law of production — as if Nature, 

 prodigal of her resources, created only to destroy; bent, as one might 

 believe, from one aspect of her dealings, upon securing the greatest 



IS See Brit. Med. Journal, July 30, 1892. 



10 I desire here to acknowledge my obligations to E. A. Fitch, Esq., F.L.S., 

 Maldon, Essex (one of the joint editors of the " Entomologist "), for the trouble he 

 has from time to time kindly taken in identifying and naming for me the various 

 insects resulting from oak and other galls. 



