320 THE ZOOLOGIST. 



expressed the view that " the most reasonable, if not the only 

 reasonable theory, is that each insect infects or inoculates the 

 leaf or other structure of the chosen plant with a poison peculiar 

 to itself." 



This, says Mr. Straton, may be taken as the view accepted 

 by scientists until Dr. Adler, of Schleswig, in the essay now 

 translated, showed conclusively that there is no foundation for 

 supposing that the gall-insect injects any irritating secretion 

 whatever ; and Beyerinck has proved that the fluid ejected by 

 the gall-fly is without taste or smell, and absolutely unirritating 

 if injected under the skin. It is probably nothing more than a 

 very mild antiseptic dressing applied to the wound made in the 

 plant. Both these authors show plainly that it is not in the 

 gall-mother, but in the larva, that we must seek for the cause of 

 gall-growth ; and that it is the nature of the salivary secretion, 

 and the manner of feeding of the larva (peculiarities inherited by 

 each species), which give the characteristic growth to the gall. 



In the monograph here translated, Dr. Adler has described 

 those oak-galls and gall-flies which are most commonly found in 

 this country, except the Devonshire marble-gall, Cynips kollari, 

 which does not occur in Germany north of the Elbe. But as this 

 is one of the most familiar galls on English oaks, the translator 

 has added a description of it in an Appendix. He has also added 

 a synoptical table of galls, which will be extremely useful to those 

 who are just taking up the subject, a short bibliography, and a 

 classified list of the Cynipidce. 



Dr. Adler's work was well worth translating, and Mr. Straton 

 has done it very well, elucidating the text with notes of his own, 

 which he has judiciously placed within brackets. On two of the 

 folding coloured plates, which have been very carefully chromo- 

 lithographed by Messrs. West, Newman & Co. from Dr. Adler's 

 drawings, are depicted a large number of galls with, in some 

 cases, the flies magnified ; and in another plate, in which the 

 figures are all drawn from photographs, we see the different 

 forms of ovipositor, with the egg, when accompanying it, drawn 

 to the same scale. The subject is one which, we can well 

 imagine, many people would find very fascinating. 



