256 MICROSCOPICAL MEMORANDA. 



which, in the recent tissue, I am unable to see* or comprehend ; if it be 

 only to be observed under the effects of decomposition or chemical re- 

 agents, then it is possible that appearances so produced may be de- 

 lusive. 



The fact of two spirals occurring in the same tubes or cells, is known 

 to every vegetablea natomist. Many species of Jungermannia possess 

 elaters of this structure ; and in the wood of the yew, the same has 

 been noticed years ago ; but in neither case, nor in any recent wood 

 that I have ever examined, is a structure to be found precisely like that 

 to be seen in the coal which I exhibited. The nearest instance occurs 

 in the wood of Drimys Winteri, which I believe was first noticed by 

 Dr. Robert Brown. Therefore I trust the justice will be done me, to 

 allow this statement to contradict that part of the paragraph in the 

 Journal, viz., "it will be obvious that Mr. Quekett was mistaken when 

 he stated his belief, in reference to his own observation, that ' nothing 

 analogous had hitherto been detected in recent woods.' " Letter to 

 the Editors. 



[The mistake as to the date of the meeting of the Microscopical So- 

 ciety, at which Mr. Quekett's observations were made, is sufficiently 

 obvious ; and with reference to the supposed coincidence of Dr. Barry's 

 and Mr. Quekett's description of vegetable fibre, the above letter ren- 

 ders it quite evident, if it were not so before, that the observations and 

 descriptions of these gentlemen regard two entirely different objects, 

 and in no respect interfere with each other. Dr. Barry refers to the 

 supposed structure of what he terms elementary fibre, and Mr. Quekett's 

 to the mode of arrangement of an organ which may or may not be com- 

 posed of Dr. Barry's double spiral filaments.] 



On the Extent of the Ova of an A earns. It may be interesting to 

 microscopic observers to be informed, that the pebbles of the gravel on 

 Blackheath and the neighbourhood, are at the present time abundantly 

 covered with the ova of the Acarus lately described by Mr. White, and 

 formerly considered as a fungus under the name of Craterium pyriforme. 



Before the late rains, these bodies were to be seen on pieces of wood 

 and many other substances, as the stalks of plants, &c., as well as on 

 the pebbles. We have lately seen specimens of the same deposit on 

 pebbles, from Lincolnshire and from Devonshire or Cornwall in the 

 neighbourhood of Plymouth ; from which it would appear to be very 

 generally distributed throughout the country. It may not impro- 

 bably perhaps prove to be the ovum of the harvest bug, (Acarus Au- 

 tumnalis of Shaw.) E. M. J. 



* I have examined the fibre of the spiral vessels of the strawberry leaf, placed in 

 a solution of corrosive sublimate and diluted alcohol, as recommended by Dr. Barry, 

 but have not yet been able to discover the bi-spiral character of the filaments. 

 E. J. Q. 



