HARDWICKE'S SCIENCE-GOSSIP. 



179 



all ornithologists will agree with me, at least as far as 

 the Somerset reported occurrence is concerned, in a 

 verdict of "not proven." I may add that I am 

 much obliged to both Mr. Dyke and Mr. Galpin for 

 so kindly writing to give Mr. Bidgood all the infor- 

 mation they could on the subject. I have not 

 written to Mr. Herridge who recorded it, as he 

 appears never to have seen the bird himself. 



Cecil Smith. 



THE ADMISSION OF CERTAIN LAND 

 SHELLS INTO THE BRITISH LIST. 



BEING away from home, I must ask Mr. SherrifT 

 Tye to excuse a very detailed answer to his 

 courteous reply (Science-Gossip, July, 1SS3, p. 146) 

 to my former observations (p. 1 12). It seems to me 

 that there is now no further cause for difference 

 between us, since Mr. Tye confesses that he quite 

 agrees with me as to the "probability" {vide top of 

 p. 146) of certain of the species under discussion 

 having been introduced by human agency. Now, 

 this is all that I wished to contend for ; and it seems 

 to me that this confession of Mr. Tye's hardly agrees 

 with his former statement, that ' ' in the absence of 

 any information to the contrary," we must regard 

 them as indigenous. I do not think that Succitiea 

 oblonga can fairly be compared with Helix villosa. 

 Had only three or four specimens (some of them 

 dead) ever been found in England, and had there not 

 been at least one inland locality, I should certainly 

 have urged "introduction" on its behalf. With 

 regard to Helix personata I may observe that my 

 conjecture, that this species at least is an introduction, 

 is so fully confirmed by Mr. Stuart's note (p. 159), 

 that probably not even Dr. Jeffreys will now retain 

 his belief in its being a native. In this case the 

 question as to whether or not a species is likely to 

 occur in Ireland which has never been found in 

 England, is not now essential to my argument, and I 

 am free to confess that in writing I overlooked the 

 two instances of this which Mr. Tye points out ; but, 

 nevertheless, I believe I am not wrong in repeating 

 that, seeing the mollusca of Ireland is as much a 

 " derivative " one as that of England, and that the 

 Irish species in their migrations must, at some time 

 or other, have crossed England, the probability at 

 least is, that they will still occur here, although, as 

 already mentioned, there are at least two well-known 

 exceptions to this. I fear I have written obscurely if 

 Mr. Tye is under the impression that I wished to 

 dispute the fact of any migration having taken place. 

 All I objected to was his statement that " the theory 

 of migration points in a N.W. direction," which I 

 hold to be a somewhat odd expression, and his 

 assertion that the species under discussion are there- 

 fore more likely to occur in the S.E. of England 



than elsewhere, the reason for which I still fail to 

 see — perhaps wrongly. As to Helix lamellata and 

 Mr. Tye's suppositions concerning it, I may remark 

 that, unless my memory greatly deceives me (I have 

 no books or notes here to refer to), I have found this 

 species in one of the latest of the Tertiary deposits of 

 Essex. I thank Mr. Tye for having called my 

 attention to his remarks on the distribution of Helix 

 cantia?ia. In conclusion, I desire again to state my 

 belief that, on account of the extremely few speci- 

 mens that have hitherto been found of the species 

 under discussion, and their striking proximity to sea- 

 ports, there is not only a probability, but every 

 probability, of their having been introduced by human 

 agency. 

 Liverpool. Robert Miller Christy. 



CURIOUS MOTION IN THE FRUIT OF THE 

 LIME-TREE {TIL/A EUROPE A, L.). 



EVERY one is familiar with the singular in- 

 florescence of the genus Tilia, in which the 

 long peduncle, really auxiliary to the large papery 

 bract, is so adnate to this for about half its length, 

 as to appear to spring from the middle. Well 

 known as are these lindens, or limes, and especially 

 the Tilia Europaa, L., I do not recall having 

 seen any mention of the use that the plant makes 

 of this scale in distributing the fruit. As the 

 globular nuts ripen, the scale becomes more dry and 

 papery. It also bends back upon itself from the 

 point where the peduncle becomes free ; it is weighted 

 as it were by the fruit-balls below ; sometimes, more- 

 over, there is a lateral twist to the wing, making it 

 not unlike the fluke of the propeller. Now when a 

 breeze disengages this apparatus, it falls by its own 

 weight, but, through the influence of the wing, at 

 once begins to revolve rapidly upon its axis, looking 

 like the governor of a steam-engine in rapid motion. 

 I take it there is here a chance for mathematical 

 research, but this is unfortunately out of my line. 

 Will not some botanist of a mechanical turn, if such 

 a being exists, study into this matter a little ? I 

 take it that the purpose of the apparatus is, as in the 

 case of the ash, to propel the fruit outside of the 

 immediate radius of the tree. So like butterflies do 

 these scale-borne nuts in the air appear, that I have 

 been repeatedly deceived by them. It seems to me 

 that the subject would reward the diligent study of 

 one who combined good powers of observation 

 with certain mathematical attainments. I would 

 add that the nuts more or less break off before the 

 disarticulation of the scale from the tree, one or two 

 only remaining, and these standing somewhat at 

 right angles to the main peduncle. May not this 

 throwing the weight to one side itself induce the 

 revolution ? 



Professor W. Bailey. 



