TRANSACTIONS OF SECTION D. 805 



2. Interim Report on the Legislative Protection of Wild Birds' Eggs. 



See Reports, p. 652. 



3. Ow the .Etiology and Life-history of some Vegetal Galls and their 

 Inhabitants.^ By G. B. Rothera. 



In tte restricted sense in which the term is here applied, galls are defined as 

 complex organisms resulting from the co-operation of a plant and an animal; and 

 to determine the extent and modus operandi of these two factors in their produc- 

 tion is one of the many interesting problems which this study presents. Though 

 abnormal with regard to the plant, inasmuch as their presence is exceptional and 

 foreign to the performance of its proper functions, galls are in themselves as normal 

 as any other organisms. Each has its own characteristic form, its special habitat, 

 and its proper office. Hence, after referring to the great diversity of these 

 organisms and their wide distribution, the writer proceeds to trace out the life- 

 history of certain typical galls, those of Cynips Kollari, Ttras tenuinaiis, and 

 Biorhiza aptera being specially dealt with. 



What is there, he asks, in the casual presence of the ovum of the gall-producing 

 insect, in the action of the developing larva, in the mechanical puncture of the 

 parent cj^nips, or in the deposit of a tiny drop of irritating fluid by which it is said 

 the ovipositing is accompanied — what is there in any one, or more, or all of these, 

 or, it may be, in the action of some other factor yet to be discovered, that impels 

 these wonder-working changes by which the gall itself is initiated and its future 

 growth and development accompanied ? Reviewing the various attempts made to 

 answer this and cognate questions, as also the arguments by which the generally 

 accepted view of the deposit by the parent cynips of a special virus is supported, 

 the author denies the alleged analogy upon which the conclusion thence arrived at 

 rests. The presence of the ovum Cnot found in any of the cases stated) may be, he 

 suggests, as necessary a factor in the production of the gall as is the deposit of a 

 specific virus ; while in many cases galls are found to result from the action of 

 other animals than terebrant hymenoptera — as, for example, of kermes, cecydomiae, 

 and acari — where no such poison-glaud as that referred to exists. Very early in 

 his investigations (now extending over a period of five-and-twenty years) the 

 writer arrived at the conclusion that another agent, as potent as that of this hypo- 

 thetical virus, was essential to the production of, at least, some species of vegetal 

 galls, such agent being the presence and action of a living larva. In illustration 

 of this the ' oak-apple ' may be taken. Here the parent cynips {Biorhiza aptera — 

 the agamic form of Terasterminalis'), b\ a dexterous use of her terebra prepara- 

 tory to ovipositing, makes a cut across the axis of a winter bud of the oak, above 

 the circlet of scales by which it is surrounded, so as to separate the cone-like 

 aper with its appendages. In the space thus prepared a variable number of 

 eggs is laid — at times as many as two hundred and fifty or more. Should these, 

 however, notwithstanding the incision, fail to be deposited, or, if laid, perish 

 during the winter, no growth, normal or abnormal, takes place from the divided 

 axis. This remains brown, dry, and inactive. If, on the other hand, healthy ova 

 are present, and these hatch out their living embryos, then, by the action of these 

 upon the dormant tissues, new and peculiar powers of growth are manifested — 

 powers which result in the production, not of a normal branch, but of an abnormal, 

 tumour-like gall. Here, then, we have a series of facts, positive and negative, 

 which point to the action of the embryo, and not to the deposit of a special virus 

 by the parent cynips, as the direct and necessary agent in the production of the 

 gall. Granting, for the sake of illustration, the existence and potency of such 

 Tirus, ought we not in such case to expect that, even in the absence of living Uirvte, 

 the normal energies of the fluid would be exerted, and a gall, destitute though it 

 might be of normal occupants, of necessity result ? In the author's long experience 

 DO facts confirmatory of this view have been met with, nor is it probable that any 

 such barren galls exist. Are we not, then, justified in discarding the hype 



' Published in cxtcnso in Xatural Science, Novembci' 1893. 



