358 NATURAL SCIENCE. Nov.. 



a factor in the production of the gall as is the deposit of a specific 

 virus ; while it must be remembered that galls, in many cases, result 

 from the action of other animals than Terebrant Hymenoptera, as, 

 for example, of Ckarmes, Cecydomia, and Acari, where no such poison- 

 gland as that referred to exists. 



Very early in our investigations Dr. Ransom and myself 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 vegetable galls, such agent being the presence and action of a 

 living larva — a conclusion communicated by me in a paper read 

 before the Natural Science Section of our then Literary and Philo- 

 sophical Society, on the 4th of April, 1877. 



Subsequently to that date, the subject received exhaustive study 

 at the hands of Dr. M. W. Beyerinck, of Utrecht, whose " Observa- 

 tions on the Early Development-Phases of some Cynips Galls " were 

 published by the Royal Academy of Sciences, at Amsterdam, in the 

 year 1882. In these, Dr. Beyerinck, as a deduction from the like 

 series of facts we had ourselves observed, submitted the opinion that, 

 in the cases referred to, the action of the Cynips larvae, and not the 

 injection by the parent Cynips of a specific virus, was the sole cause 

 of gall-formation. 1 -* 



Whether so or not, is in a measure, at least, doubtful. This, 

 however, I think we may safely conclude, namely : that while, on the 

 one hand, in those chemical and other forces which produce growth, 

 greater activity is induced by the stimulus of the injected fluid — 

 assuming such fluid to be actually present — so, on the other, those 

 mechanical conditions which determine form in organic beings are 

 furnished, to a large extent, by the contact of the included ovum, and 

 by the activities of the embryonic larva. 



As the nut-gall approaches maturity — which, under favourable 

 circumstances, it may do within a fortnight or three weeks of its first 

 appearance, early in July — the cellular tissue of which it is at first 

 composed becomes differentiated into five principal layers. The 

 innermost of these, surrounding the central chamber, and known as 

 the alimentary layer, is composed of thin-walled cells, filled with 

 protoplasm, minute starch' granules, oil, and albumen. This layer 

 disappears pari passu with the developing larva, which finds in its 

 substance the food-elements necessary to its growth. At first the 

 chamber-walls are in direct contact with the very young larva, whose 

 increase is, in the first instance, due to absorption or to suction. 



Next in order is the protective layer, or Couclic protectrice, built up 

 of hard, compact cells, with strong, thick walls. Around these are 

 arranged, in radial series, bundles of elongated cells, forming a sort of 

 chevaux dc jvisc or abatis — the whole constituting a fortified casemate 

 or stronghold for the protection of the occupant and her commissariat 



14 See " Beobachtungen liber die ersten entwicklungsphasen einiger Cynipiden 

 gallon " von Dr. M. W. Beyerinck, p. 8. 



